From 1c67127d1d13e55bb709935a4850b92f8f7b77cf Mon Sep 17 00:00:00 2001
From: Akamaki <97360908+akmed772@users.noreply.github.com>
Date: Mon, 16 Feb 2026 00:57:23 +0900
Subject: [PATCH 01/11] ps55da2: avoid resizing when video output is disabled

---
 src/video/vid_ps55da2.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/src/video/vid_ps55da2.c b/src/video/vid_ps55da2.c
index 3df73f92c..a1d7fe25f 100644
--- a/src/video/vid_ps55da2.c
+++ b/src/video/vid_ps55da2.c
@@ -2352,12 +2352,8 @@ da2_recalctimings(da2_t *da2)
     da2->render     = da2_render_blank;
     /* determine display mode */
     // if (da2->attr_palette_enable && (da2->attrc[0x1f] & 0x08))
-    /* if output disabled or VGA passthrough */
-    if (da2->ioctl[LS_MODE] & 0x02 || !(da2->attrc[LV_COMPATIBILITY] & 0x08)) {
-        da2->render = da2_render_blank;
-        // return;
     /* 16 color graphics mode */
-    } else if (!(da2->ioctl[LS_MODE] & 0x01)) {
+    if (!(da2->ioctl[LS_MODE] & 0x01)) {
         da2->hdisp *= 16;
         da2->char_width = 13;
         if (da2->crtc[LC_VIEWPORT_PRIORITY] & 0x80) {
@@ -2383,6 +2379,9 @@ da2_recalctimings(da2_t *da2)
         da2->hdisp *= 13;
         da2->char_width = 13;
     }
+    /* if output disabled or VGA passthrough */
+    if (da2->ioctl[LS_MODE] & 0x02 || !(da2->attrc[LV_COMPATIBILITY] & 0x08)) 
+        da2->render = da2_render_blank;
 
     if (da2->vblankstart < da2->dispend)
         da2->dispend = da2->vblankstart;

From c3db24162131f7dba9b76b3015f1ddb0a55ccd45 Mon Sep 17 00:00:00 2001
From: Akamaki <97360908+akmed772@users.noreply.github.com>
Date: Thu, 19 Feb 2026 11:00:09 +0900
Subject: [PATCH 02/11] IBM 5550: Added font 16 emulation

---
 src/include/86box/machine.h |   4 +-
 src/machine/m_xt_ibm5550.c  | 392 ++++++++++++++++++++++++++++++------
 src/machine/machine_table.c |   2 +-
 3 files changed, 331 insertions(+), 67 deletions(-)

diff --git a/src/include/86box/machine.h b/src/include/86box/machine.h
index af39e17e4..8a631f40a 100644
--- a/src/include/86box/machine.h
+++ b/src/include/86box/machine.h
@@ -1521,7 +1521,9 @@ extern int             machine_xt_lxt3_init(const machine_t *);
 extern int             machine_xt_compaq_deskpro_init(const machine_t *);
 
 /* m_xt_ibm5550.c */
-
+#ifdef EMU_DEVICE_H
+extern const device_t  ibm5550_vid_device;
+#endif
 extern int             machine_xt_ibm5550_init(const machine_t *);
 
 /* m_xt_t1000.c */
diff --git a/src/machine/m_xt_ibm5550.c b/src/machine/m_xt_ibm5550.c
index fed353344..089de761f 100644
--- a/src/machine/m_xt_ibm5550.c
+++ b/src/machine/m_xt_ibm5550.c
@@ -74,6 +74,8 @@
 #define EPOCH_MASK_VRAM            0x3ffff       /* 0xFFFFF */
 // #define EPOCH_MASK_VRAMPLANE       0x1ffff       /* 0x1FFFF */
 #define EPOCH_PIXELCLOCK           40000000.0    /* 40 MHz interlaced */
+#define EPOCH_CONFIG_MONO16 0 /* Model 5551-Axx (Font 16, monochrome) */
+#define EPOCH_CONFIG_MONO24 1 /* Model 5551-Bxx (Font 24, monochrome) */
 
 #define LC_INDEX                0x3D0
 #define LC_DATA                 0x3D1
@@ -156,11 +158,11 @@ enum epoch_nvr_ADDR {
 };
 
 #ifndef RELEASE_BUILD
-// #define ENABLE_EPOCH_LOG 1
+#define ENABLE_EPOCH_LOG 1
 #endif
 
 #ifdef ENABLE_EPOCH_LOG
-// #define ENABLE_EPOCH_DEBUGIO 1
+#define ENABLE_EPOCH_DEBUGIO 1
 // #define ENABLE_EPOCH_DEBUGKBD 1
 int epoch_do_log = ENABLE_EPOCH_LOG;
 
@@ -236,6 +238,7 @@ typedef struct epoch_t {
     int      cursorvisible, cursoron, blink;
     int      scrollcache;
     int      char_width;
+    int      font24;
 
     int firstline, lastline;
     int firstline_draw, lastline_draw;
@@ -307,6 +310,30 @@ The IBM 5550 has different IRQ assignments like the 6580 Displaywriter System.
 | FC000h        | ROM                                                   | 
 */
 
+#ifdef ENABLE_EPOCH_LOG
+// #include <ctype.h>
+// static int dumpno = 0x61;
+// static void
+// epoch_dumpvram(void *priv)
+// {
+//             FILE *fp;
+//     epoch_t *epoch = (epoch_t *) priv;
+//             char str1[64] = "epoch_vramvm_";
+//             char str2[3] = {0x30, 0x30, 0};
+//             if (!isalnum(dumpno))
+//                return;
+//             str2[0] = dumpno;
+//             dumpno++;
+//             str2[1] = (epoch->crtmode & 0xf) + 0x30;
+//             strcat(str1,str2);
+//             fp = fopen(str1, "wb");
+//             if (fp != NULL) {
+//                 fwrite(epoch->vram, EPOCH_SIZE_VRAM, 1, fp);
+//                 fclose(fp);
+//             }
+// }
+#endif
+
 static void
 epoch_out(uint16_t addr, uint16_t val, void *priv)
 {
@@ -370,7 +397,11 @@ epoch_out(uint16_t addr, uint16_t val, void *priv)
             // mem_mapping_enable(&epoch->paritymap);
             break;
         case 0x3D8:
+            /* Bit 3: Font access in read, Bit 1: graphic mode, Bit 0: Font access in write */
             epoch->crtmode = val;
+#ifdef ENABLE_EPOCH_LOG
+            // epoch_dumpvram(epoch);
+#endif
             epoch_recalctimings(epoch);
             // epoch->attrff ^= 1;
             break;
@@ -613,22 +644,43 @@ epoch_inw(uint16_t addr, void *priv)
     return temp;
 }
 
-/* Get character line pattern from jfont rom or gaiji volatile memory */
+/* Get font pattern in a line from video memory */
 static uint32_t
 getfont_ps55dbcs(int32_t code, int32_t line, void *priv)
 {
-    epoch_t   *epoch   = (epoch_t *) priv;
+    epoch_t *epoch = (epoch_t *) priv;
     uint32_t font  = 0;
-	if (code < 1536) {
-		code *= 0x80;
-		font = epoch->vram[code + line * 4];
-		font <<= 8;
-		font |= epoch->vram[code + line * 4 + 1];
-		font <<= 8;
-		font |= epoch->vram[code + line * 4 + 2];
-		font <<= 8;
-		font |= epoch->vram[code + line * 4 + 3];
-    } else 
+    if (code < 1536) {
+        code *= 0x80;
+        code += line * 4;
+        if (epoch->font24) { /* Font 24 (2 x 13 x 29) */
+            font = epoch->vram[code];
+            font <<= 8;
+            code++;
+            font |= epoch->vram[code];
+            font <<= 8;
+            code++;
+            font |= epoch->vram[code];
+            font <<= 8;
+            code++;
+            font |= epoch->vram[code];
+        } else { /* Font 16 (2 x 9 x 21) */
+            int bitnum = code & 0x7;
+            font = epoch->vram[code];
+            font <<= 8;
+            font |= (epoch->vram[(code >> 3) + 0x20000 ] << (7 - bitnum)) & 0xff; /* get 9th bit */
+            // font &= 0xffffff80;
+            // font |= epoch->vram[code + line * 4 + 1];
+            font <<= 8;
+            code++;
+            font |= epoch->vram[code];
+            font <<= 8;
+            bitnum = code & 0x7;
+            font |= (epoch->vram[(code >> 3) + 0x20000 ] << (7 - bitnum)) & 0xff; /* get 9th bit */
+            font &= 0xff80ff80;
+            // font |= epoch->vram[code + line * 4 + 3];
+        }
+    } else
         font = EPOCH_INVALIDACCESS32;
     return font;
 }
@@ -676,12 +728,13 @@ epoch_render_text(epoch_t *epoch)
         uint8_t   chr, attr;
         int       fg, bg;
         uint32_t  chr_dbcs;
+        int       underscore_y = (epoch->font24) ? 28 : 20;
         int       chr_wide = 0;
         // int       colormode = ((epoch->attrc[LV_PAS_STATUS_CNTRL] & 0x80) == 0x80);
         int       colormode = 0;
         // epoch_log("displ: %x, first: %x, epochma: %x, epochsc: %x\n", 
         //     epoch->displine , epoch->firstline_draw, epoch->memaddr, epoch->scanline);
-        for (x = 0; x < epoch->hdisp; x += 13) {
+        for (x = 0; x < epoch->hdisp; x += epoch->char_width) {
             chr  = epoch->cram[(epoch->memaddr) & EPOCH_MASK_CRAM];
             attr = epoch->cram[(epoch->memaddr + 1) & EPOCH_MASK_CRAM];
             // if(chr!=0x20) epoch_log("chr: %x, attr: %x    ", chr, attr);
@@ -713,7 +766,7 @@ epoch_render_text(epoch_t *epoch)
                 // if(chr!=0x20) epoch_log("chr: %x, %x, %x, %x, %x    ", chr, attr, fg, epoch->egapal[fg], epoch->pallook[epoch->egapal[fg]]);
             }
             /* Draw character */
-            for (uint32_t n = 0; n < 13; n++)
+            for (uint32_t n = 0; n < epoch->char_width; n++)
                 p[n] = epoch->pallook[epoch->egapal[bg]]; /* draw blank */
             /*  SBCS or DBCS left half */
             if (chr_wide == 0) {
@@ -729,23 +782,37 @@ epoch_render_text(epoch_t *epoch)
                     /* Get the font pattern */
                     uint32_t font = getfont_ps55dbcs(chr_dbcs, epoch->scanline, epoch);
                     /* Draw 13 dots */
-                    for (uint32_t n = 0; n < 13; n++) {
+                    for (uint32_t n = 0; n < epoch->char_width; n++) {
                         p[n] = epoch->pallook[epoch->egapal[(font & 0x80000000) ? fg : bg]];
                         font <<= 1;
                     }
                 } else {
                     /* the char code is SBCS (ANK) */
                     uint32_t fontbase;
+                    uint16_t font;
                     if (attr & 0x02) /* second map of SBCS font */
                         fontbase = EPOCH_VRAM_SBEX;
                     else
                         fontbase = EPOCH_VRAM_SBCS;
-                    uint16_t font = epoch->vram[fontbase + chr * 0x80 + epoch->scanline * 4]; /* w13xh29 font */
-                    font <<= 8;
-                    font |= epoch->vram[fontbase + chr * 0x80 + epoch->scanline * 4 + 1]; /* w13xh29 font */
+                    if (epoch->font24) {
+                        font = epoch->vram[fontbase + chr * 0x80 + epoch->scanline * 4 + 2]; /* w13xh29 font */
+                        font <<= 8;
+                        font |= epoch->vram[fontbase + chr * 0x80 + epoch->scanline * 4 + 3];
+                    } else {
+                        int bitnum;
+                        fontbase = (fontbase & 0x1ffff) + chr * 0x80 + epoch->scanline * 4;
+                        bitnum = fontbase & 0x7;
+                        font = epoch->vram[fontbase + 2]; /* w9xh21 font */
+                        font <<= 8;
+                        // font |= epoch->vram[fontbase + chr * 0x80 + epoch->scanline * 4 + 3];
+                        fontbase >>= 3;
+                        fontbase += 0x20000; /* real: C0000h */
+                        font |= epoch->vram[fontbase] << (8 + 7 - bitnum);
+                        // if(chr!=0x20) epoch_log("faddr: %x, scline: %x, chr: %x, font: %x    ", fontbase + chr * 0x80 + epoch->scanline * 4, epoch->scanline, chr, font);
+                    }
                     // if(chr!=0x20) epoch_log("memaddr: %x, scanline: %x, chr: %x, font: %x    ", epoch->memaddr, epoch->scanline, chr, font);
                     /* Draw 13 dots */
-                    for (uint32_t n = 0; n < 13; n++) {
+                    for (uint32_t n = 0; n < epoch->char_width; n++) {
                         p[n] = epoch->pallook[epoch->egapal[(font & 0x8000) ? fg : bg]];
                         font <<= 1;
                     }
@@ -755,15 +822,15 @@ epoch_render_text(epoch_t *epoch)
             else {
                 uint32_t font = getfont_ps55dbcs(chr_dbcs, epoch->scanline, epoch);
                 /* Draw 13 dots */
-                for (uint32_t n = 0; n < 13; n++) {
+                for (uint32_t n = 0; n < epoch->char_width; n++) {
                     p[n] = epoch->pallook[epoch->egapal[(font & 0x8000) ? fg : bg]];
                     font <<= 1;
                 }
                 chr_wide = 0;
             }
             /* Line 28 (Underscore) Note: Draw this first to display blink + vertical + underline correctly. */
-            if (epoch->scanline == 28 && attr & 0x40 && !colormode) { /* Underscore only in monochrome mode */
-                for (uint32_t n = 0; n < 13; n++)
+            if (epoch->scanline == underscore_y && attr & 0x40 && !colormode) { /* Underscore only in monochrome mode */
+                for (uint32_t n = 0; n < epoch->char_width; n++)
                     p[n] = epoch->pallook[epoch->egapal[fg]]; /* under line (white) */
             }
             /* Column 1 (Vertical Line) */
@@ -771,14 +838,14 @@ epoch_render_text(epoch_t *epoch)
                 p[0] = epoch->pallook[epoch->egapal[2]]; /* vertical line (white) */
             }
             if (epoch->scanline == 0 && attr & 0x20) { /* HGrid */
-                for (uint32_t n = 0; n < 13; n++)
+                for (uint32_t n = 0; n < epoch->char_width; n++)
                     p[n] = epoch->pallook[epoch->egapal[2]]; /* horizontal line (white) */
             }
             /* Drawing text cursor */
             drawcursor = ((epoch->memaddr == epoch->cursoraddr) && epoch->cursorvisible && epoch->cursoron);
             if (drawcursor && epoch->scanline >= epoch->crtc[LC_CURSOR_ROW_START] && epoch->scanline <= epoch->crtc[LC_CURSOR_ROW_END]) {
                 // int cursorwidth = (epoch->crtc[LC_COMPATIBILITY] & 0x20 ? 26 : 13);
-                int cursorwidth = 13;
+                int cursorwidth = epoch->char_width;
                 int cursorcolor = 2; /* Choose color 2 if mode 8 */
                 fg              = ((attr & 0x08) ? 3 : 2);
                 bg              = 0;
@@ -793,7 +860,7 @@ epoch_render_text(epoch_t *epoch)
                         p[n] = (p[n] == epoch->pallook[epoch->egapal[bg]]) ? epoch->pallook[epoch->egapal[cursorcolor]] : p[n];
             }
             epoch->memaddr += 2;
-            p += 13;
+            p += epoch->char_width;
         }
     }
 }
@@ -905,8 +972,13 @@ epoch_recalctimings(epoch_t *epoch)
 
     /* determine display mode */
     if (epoch->crtmode & 0x02) {
-        epoch->hdisp *= 16;
-        epoch->char_width = 16;
+        if (epoch->font24) {
+            epoch->hdisp *= 16;
+            epoch->char_width = 16;
+        } else {
+            epoch->hdisp *= 11;
+            epoch->char_width = 11;
+        }
         /* PS/55 8-color */
         epoch_log("Set videomode to PS/55 4 bpp graphics.\n");
         epoch->render            = epoch_render_color_4bpp;
@@ -916,8 +988,13 @@ epoch_recalctimings(epoch_t *epoch)
         epoch_log("Set videomode to PS/55 Mode 8/E text.\n");
         epoch->render            = epoch_render_text;
         epoch->vram_display_mask = EPOCH_MASK_CRAM;
-        epoch->hdisp *= 13;
-        epoch->char_width = 13;
+        if (epoch->font24) {
+            epoch->hdisp *= 13;
+            epoch->char_width = 13;
+        } else {
+            epoch->hdisp *= 9;
+            epoch->char_width = 9;
+        }
     }
     if (epoch->crtmode & 0x08)
         epoch->render = epoch_render_blank;
@@ -1114,55 +1191,211 @@ epoch_vram_write(uint32_t addr, uint8_t val, void *priv)
 {
     epoch_t *epoch = (epoch_t *) priv;
     // if ((addr & ~0xfff) != 0xE0000) return;
-    addr -= 0xA0000;
+    // epoch_log("epoch_vw: %x %x\n", addr, val);
     addr &= EPOCH_MASK_VRAM;
     epoch->vram[addr] = val;
     epoch->fullchange = changeframecount;
     // if(val == 0x66)
     //         epoch_log("66 %04X:%04X %04X:%04X>%04X:%04X\n", cs >> 4, cpu_state.pc, DS, SI,ES,DI);
 }
-static void
-epoch_vram_writeb(uint32_t addr, uint8_t val, void *priv)
-{
-    epoch_t *epoch = (epoch_t *) priv;
-    // epoch_log("%04X:%04X epoch_vram_writeb: %x, val %x\n", cs >> 4, cpu_state.pc, addr, val);
-    cycles -= video_timing_write_b;
-    epoch_vram_write(addr, val, epoch);
-}
-static void
-epoch_vram_writew(uint32_t addr, uint16_t val, void *priv)
-{
-    // epoch_log("%04X:%04X epoch_vram_writew: %x, val %x\n", cs >> 4, cpu_state.pc, addr, val);
-    epoch_t *epoch = (epoch_t *) priv;
-    cycles -= video_timing_write_w;
-    epoch_vram_write(addr, val & 0xff, epoch);
-    epoch_vram_write(addr + 1, val >> 8, epoch);
-}
-
 static uint8_t
 epoch_vram_read(uint32_t addr, void *priv)
 {
     epoch_t *epoch = (epoch_t *) priv;
     // if ((addr & ~epoch_MASK_CRAM) != 0xE0000)
     //     return epoch_INVALIDACCESS8;
-    addr -= 0xA0000;
     addr &= EPOCH_MASK_VRAM;
     return epoch->vram[addr];
 }
+
+static void
+epoch_vram_writeb(uint32_t addr, uint8_t val, void *priv)
+{
+    epoch_t *epoch = (epoch_t *) priv;
+//    epoch_log("%04X:%04X epoch_vwb: %x, val %x\n", cs >> 4, cpu_state.pc, addr, val);
+    cycles -= video_timing_write_b;
+    // return;
+//    epoch_vram_write(addr, val, epoch);
+}
+static void
+epoch_vram_writew(uint32_t addr, uint16_t val, void *priv)
+{
+    epoch_t *epoch = (epoch_t *) priv;
+    // uint8_t convert[8] = {0, 2, 8, 8, 1, 3, 8, 8};/* only even chars */
+    //uint8_t convert[8] = {8, 8, 0, 2, 8, 8, 1, 3};/* only even chars */
+    // uint8_t convert[8] = {0, 1, 2, 3, 4, 5, 6, 7};/* all but alt */
+    // uint8_t convert[8] = {0, 1, 2, 3, 8, 8, 8, 8};/* even alt */
+    // uint8_t convert[8] = {8, 8, 8, 8, 0, 1, 2, 3};/* even alt */
+    // uint8_t convert[8] = {0, 4, 1, 5, 2, 6, 3, 7};/* all but pos+-1 */
+    // uint8_t convert[8] = {8, 8, 4, 6, 8, 8, 5, 7};/* only odd (0) */
+    // uint8_t convert[8] = {8, 8, 0, 2, 8, 8, 1, 3};/* only even */
+    // uint8_t convert[8] = {4, 6, 8, 8, 5, 7, 8, 8};/* only odd (0) */
+    // uint8_t convert[8] = {8, 4, 6, 8, 8, 5, 7, 8};/* none */
+    // epoch_log("%04X:%04X epoch_vww: %x, val %x DS %x SI %x ES %x DI %x %x\n", cs >> 4, cpu_state.pc, addr, val,DS,SI,ES,DI, epoch->crtc[LC_INTERLACE_AND_SKEW]);
+    epoch_log("%04X:%04X epoch_vww: %x, val %x cm %x\n", cs >> 4, cpu_state.pc, addr, val, epoch->crtmode);
+    cycles -= video_timing_write_w;
+    addr -= 0xA0000;
+    // addr &= 0xfffffffe;
+    // if (0) {
+    if (!(epoch->crtmode & 0x02) && !(epoch->font24)) {
+        uint32_t toaddr, bitnum;
+        // if (addr < 0xd0000) {
+        //     int index = (addr - 0xA0000) >> 7; /* 128 bytes per char */
+        //     addr &= 0x007f;
+        //     addr += 0xA0000 + 84 * index;
+        // epoch_log("%x %x\n", addr, index);
+        // } else if (addr >= 0xD8000) {
+        //     int index = (addr - 0xD8000) >> 7; /* 128 bytes per char */
+        //     addr &= 0x007f;
+        //     if (addr & 2) return;
+        //     addr >>= 1;
+        //     addr += 0xC0000 + 42 * index;
+        // epoch_log("%x %x\n", addr, index);
+        // } else
+        //     return;
+
+        // if (addr < 0xd0000) {
+        //     addr -= 0xA0000;
+        //     if (addr & 2)
+        //         return;
+        //     addr >>= 1;
+        //     addr += 0xA0000;
+        // } else if (addr >= 0xD8000) {
+        //     addr -= 0xD8000;
+        //     if (addr & 2)
+        //         return;
+        //     addr >>= 1;
+        //     addr += 0xD8000;
+        // } else
+        //     return;
+
+        // addr >>= 1;
+        // if(addr & 0x02)
+        //     addr--;
+        // addr ^= 0x06;
+        //addr &= 0xffffd;/* 1101 */
+        // addr >>= 1;
+        
+        // if (convert[(addr + 0) & 7] > 7)
+        //     return;  
+        // epoch_vram_write((addr & 0xffff8) + convert[(addr + 0) & 7], val & 0xff, epoch);
+        // epoch_vram_write((addr & 0xffff8) + convert[(addr + 1) & 7], val >> 8, epoch);
+
+        /* rw one word with 9 bits */
+        /* virtual: 20000h (0010b, 0011b) -> real: 00001h (0000b, 0001b) */
+        toaddr = addr;
+        if (addr & 2)
+            toaddr--;
+        if (addr & 0x20000)
+            toaddr+=2;
+        toaddr &= 0xdffff;
+
+        //addr >>= 1;
+        
+        epoch_vram_write(toaddr, val & 0xff, epoch);
+        // epoch_log("%x %x ", toaddr, val);
+        /* get 9th bit */
+        bitnum =  addr & 0x7;
+        val >>= 15;
+        val <<= bitnum;
+        addr >>= 3;
+        addr += 0x20000; /* real: C0000h */
+        val |= epoch_vram_read(addr, epoch) & ~(1 << bitnum);/* mask to update one bit */
+        epoch_vram_write(addr, val, epoch);
+        // epoch_log("%x %x\n", addr, val);
+    } else {/* is graphic mode */
+        epoch_vram_write(addr, val & 0xff, epoch);
+        epoch_vram_write(addr + 1, val >> 8, epoch);
+    }
+    // epoch_log("%x %x\n", addr, addr + 1);
+}
+
 static uint8_t
 epoch_vram_readb(uint32_t addr, void *priv)
 {
     epoch_t *epoch = (epoch_t *) priv;
     cycles -= video_timing_read_b;
-    return epoch_vram_read(addr, epoch);
+    // return 0xff;
+ //   epoch_log("%04X:%04X epoch_vrb: %x, val %x\n", cs >> 4, cpu_state.pc, addr, epoch_vram_read(addr, epoch));
+    // return epoch_vram_read(addr, epoch);
 }
 
 static uint16_t
 epoch_vram_readw(uint32_t addr, void *priv)
 {
     epoch_t *epoch = (epoch_t *) priv;
+    // uint8_t convert[8] = {0, 2, 4, 6, 1, 3, 5, 7};/* all but pos+-1 */
+    // uint8_t convert[8] = {0, 4, 8, 8, 8, 8, 8, 8};/* all but pos+-1 */
     cycles -= video_timing_read_w;
-    return epoch_vram_read(addr, epoch) | (epoch_vram_read(addr + 1, epoch) << 8);
+    addr -= 0xA0000;
+   epoch_log("%04X:%04X epoch_vrw: %x cm %x\n", 
+    cs >> 4, cpu_state.pc, addr, epoch->crtmode);
+    // addr &= 0xfffffffe;
+    //read 0->0,1 2->2,3 4->4,5 6->6,7
+    //read 0->0,2 2->1,3 4->4,6 6->5,7
+    // if (0) {
+    if (!(epoch->crtmode & 0x02) && !(epoch->font24)) {
+        uint16_t ret;
+        uint32_t bitnum;
+        uint32_t toaddr;
+        // if (addr < 0xd0000) {
+        //     int index = (addr - 0xA0000) >> 7; /* 128 bytes per char */
+        //     addr &= 0x007f;
+        //     addr += 0xA0000 + 84 * index;
+        // epoch_log("%x %x %x\n", addr, index, epoch_vram_read(addr, epoch) | (epoch_vram_read(addr + 1, epoch) << 8));
+        // } else if (addr >= 0xD8000) {
+        //     int index = (addr - 0xD8000) >> 7; /* 128 bytes per char */
+        //     addr &= 0x007f;
+        //     if (addr & 2) return EPOCH_INVALIDACCESS16;
+        //     addr >>= 1;
+        //     addr += 0xC0000 + 42 * index;
+        // epoch_log("%x %x %x\n", addr, index, epoch_vram_read(addr, epoch) | (epoch_vram_read(addr + 1, epoch) << 8));
+        // } else
+        //     return EPOCH_INVALIDACCESS16;
+
+        // if (addr < 0xd0000) {
+        //     addr -= 0xA0000;
+        //     if (addr & 2)
+        //         return EPOCH_INVALIDACCESS16;
+        //     addr >>= 1;
+        //     addr += 0xA0000;
+        // } else if (addr >= 0xD8000) {
+        //     addr -= 0xD8000;
+        //     if (addr & 2)
+        //         return EPOCH_INVALIDACCESS16;
+        //     addr >>= 1;
+        //     addr += 0xD8000;
+        // } else
+        //         return EPOCH_INVALIDACCESS16;
+
+        // if(addr & 0x02)
+        //     addr--;
+        // // addr ^= 0x06;
+        // addr >>= 1;
+
+        // if (convert[(addr + 0) & 7] > 7)
+        //     return 0;  
+        // return epoch_vram_read((addr & 0xffff8) + convert[addr & 7], epoch) | (epoch_vram_read((addr & 0xffff8) + convert[(addr + 1) & 7], epoch) << 8);
+        
+        /* rw one word with 9 bits */
+        /* virtual: 20000h (0010b, 0011b) -> real: 00001h (0000b, 0001b) */
+        toaddr = addr; /* 1101 */
+        if (addr & 2)
+            toaddr--;
+        if (addr & 0x20000)
+            toaddr+=2;
+        toaddr &= 0xdffff;
+        ret = epoch_vram_read(toaddr, epoch);
+        /* get 9th bit */
+        bitnum =  addr & 0x7;
+        addr >>= 3;
+        addr += 0x20000; /* real: C0000h */
+        ret |= (epoch_vram_read(addr, epoch) << (8 + 7 - bitnum)) & 0x8000;
+        return ret;
+        // return epoch_vram_read(addr, epoch) | (epoch_vram_read(addr + 1, epoch) << 8);
+    } else {/* is graphic mode */
+        return epoch_vram_read(addr, epoch) | (epoch_vram_read(addr + 1, epoch) << 8);
+    }
 }
 
 
@@ -1327,8 +1560,10 @@ x1xx xxxx: No floppy drive
 1xxx xxxx: No (bootable?) hard drive
 */
         case 0xA2:
-            ret = 0xA8;/* Mono 24 */
-            // ret = 0xA2;/* Mono 16 */
+            if (epoch->font24)
+                ret = 0xA8; /* Mono 24 */
+            else
+                ret = 0xA2; /* Mono 16 */
             break;
 /*
 I/O A3h R: 
@@ -1502,7 +1737,7 @@ static void
 kbd_epoch_adddata(uint16_t val)
 {
     key_queue[key_queue_end] = val;
-    epoch_kbdlog("epochkbd: %02X added to key queue at %i\n",
+    epoch_log("epochkbd: %02X added to key queue at %i\n",
             val, key_queue_end);
     key_queue_end = (key_queue_end + 1) & 0x0f;
 }
@@ -1703,6 +1938,7 @@ kbd_close(void *priv)
 
     /* Stop the timer. */
     timer_disable(&kbd->send_delay_timer);
+    mouse_close();
 
     /* Disable scanning. */
     keyboard_scan = 0;
@@ -1967,10 +2203,12 @@ epoch_reset(void *priv)
     epoch->parityenabled = 1;
     epoch->lowmemorydisabled = 1;
     epoch->crtioenabled = 0;
+    mem_mapping_disable(&epoch->cmap);
+    mem_mapping_disable(&epoch->vmap);
     // epoch->attrc[LV_CURSOR_COLOR]    = 0x0f;                   /* cursor color */
     epoch->crtc[LC_HORIZONTAL_TOTAL] = 103;    /* Horizontal Total */
     epoch->crtc[LC_VERTICAL_TOTAL]  = 26;    /* Vertical Total (These two must be set before the timer starts.) */
-    epoch->crtmode = 0x08;
+    epoch->crtmode = 0;
     epoch->vram_display_mask = EPOCH_MASK_CRAM;
     // epoch->plane_mask = 1;
     epoch->oddeven = 0;
@@ -2080,8 +2318,6 @@ epoch_init(UNUSED(const device_t *info))
 
     epoch->epochconst = (uint64_t) ((cpuclock / EPOCH_PIXELCLOCK) * (double) (1ull << 32));
 
-    epoch_reset(epoch);
-    
     mem_mapping_add(&epoch->cmap, 0xE0000, 0x1000, epoch_cram_readb, epoch_cram_readw, NULL,
         epoch_cram_writeb, epoch_cram_writew, NULL, NULL, MEM_MAPPING_EXTERNAL, epoch);
     mem_mapping_add(&epoch->vmap, 0xA0000, 0x40000, epoch_vram_readb, epoch_vram_readw, NULL,
@@ -2089,8 +2325,6 @@ epoch_init(UNUSED(const device_t *info))
     // mem_mapping_add(&epoch->fontcard.map, 0xF0000, 0xC000, epoch_font_readb, NULL, NULL,
     //     epoch_font_writeb, NULL, NULL, NULL, MEM_MAPPING_EXTERNAL, epoch);
 
-    mem_mapping_disable(&epoch->cmap);
-    mem_mapping_disable(&epoch->vmap);
     // mem_mapping_disable(&epoch->fontcard.map);
     mem_mapping_add(&epoch->paritymap, 0, 0xA0000, epoch_parity_readb, epoch_parity_readw, NULL,
         epoch_parity_writeb, epoch_parity_writew, NULL, NULL, MEM_MAPPING_CACHE, epoch);
@@ -2106,10 +2340,14 @@ epoch_init(UNUSED(const device_t *info))
     // io_sethandler(0x160, 0x0010,
     //               epoch_misc_in, NULL, NULL, epoch_misc_out, NULL, NULL, epoch);
 
+    epoch_reset(epoch);
+    
     timer_add(&epoch->timer, epoch_poll, epoch, 1);
 
     epoch_nvr_init(epoch, 17);
 
+    epoch->font24 = device_get_config_int("model");
+
     return epoch;
 }
 
@@ -2138,6 +2376,7 @@ epoch_close(void *priv)
     // }
     fp = fopen("epoch_daregs.txt", "w");
     if (fp != NULL) {
+            fprintf(fp, "3d8(crtmode) %02X\n", epoch->crtmode);
         // for (uint8_t i = 0; i < 0x10; i++)
         //     fprintf(fp, "3e1(ioctl) %02X: %4X %d\n", i, epoch->ioctl[i], epoch->ioctl[i]);
         // for (uint8_t i = 0; i < 0x20; i++)
@@ -2186,8 +2425,31 @@ epoch_force_redraw(void *priv)
     epoch->fullchange = changeframecount;
 }
 
-static const device_t epoch_device = {
-    .name          = "IBM 5550 (Epoch) Video Controller",
+static const device_config_t epoch_config[] = {
+    // clang-format off
+    {
+        .name        = "model",
+        .description = "Model",
+        .type        = CONFIG_SELECTION,
+        .default_int = EPOCH_CONFIG_MONO24,
+        .selection   = {
+            {
+                .description = "A (Font 16)",
+                .value = EPOCH_CONFIG_MONO16
+            },
+            {
+                .description = "B (Font 24)",
+                .value = EPOCH_CONFIG_MONO24
+            },
+            { .description = "" }
+        }
+    },
+    { .name = "", .description = "", .type = CONFIG_END }
+    // clang-format on
+};
+
+const device_t ibm5550_vid_device = {
+    .name          = "IBM 5550 Video Adapter",
     .internal_name = "ibm5550vid",
     .flags         = DEVICE_ISA,
     .local         = 0,
@@ -2197,7 +2459,7 @@ static const device_t epoch_device = {
     .available     = NULL,
     .speed_changed = epoch_speed_changed,
     .force_redraw  = epoch_force_redraw,
-    .config        = NULL
+    .config        = epoch_config
 };
 
 static void
@@ -2258,7 +2520,7 @@ machine_xt_ibm5550_init(const machine_t *model)
     pit_ibm5550_init();
     nmi_mask = 0;
 
-    device_add(&epoch_device);
+    device_add(&ibm5550_vid_device);
 
     device_add(&lpt_port_device);
     serial_t *uart = device_add(&ns8250_device);
diff --git a/src/machine/machine_table.c b/src/machine/machine_table.c
index 85b09676e..2e76f5a24 100644
--- a/src/machine/machine_table.c
+++ b/src/machine/machine_table.c
@@ -2728,7 +2728,7 @@ const machine_t machines[] = {
         .kbd_device               = NULL,
         .fdc_device               = NULL,
         .sio_device               = NULL,
-        .vid_device               = NULL,
+        .vid_device               = &ibm5550_vid_device,
         .snd_device               = NULL,
         .net_device               = NULL
     },

From 0a4b44184affb8abf55017e933b2079b57577e2f Mon Sep 17 00:00:00 2001
From: Akamaki <97360908+akmed772@users.noreply.github.com>
Date: Thu, 19 Feb 2026 11:04:37 +0900
Subject: [PATCH 03/11] IBM 5550: comment out unused code

---
 src/machine/m_xt_ibm5550.c | 54 ++++++++++++++++++++------------------
 1 file changed, 28 insertions(+), 26 deletions(-)

diff --git a/src/machine/m_xt_ibm5550.c b/src/machine/m_xt_ibm5550.c
index 089de761f..ff369dede 100644
--- a/src/machine/m_xt_ibm5550.c
+++ b/src/machine/m_xt_ibm5550.c
@@ -79,8 +79,6 @@
 
 #define LC_INDEX                0x3D0
 #define LC_DATA                 0x3D1
-#define LS_ENABLE               0x3D2
-#define LS_DISABLE              0x3D3
 #define LC_HORIZONTAL_TOTAL     0x00 /* -1 */
 #define LC_HORIZONTAL_DISPLAYED 0x01
 #define LC_H_SYNC_POSITION      0x02
@@ -99,6 +97,10 @@
 #define LC_CURSOR_LOC_LOWJ      0x0F
 #define LC_LIGHT_PEN_HIGH       0x10
 #define LC_LIGHT_PEN_LOW        0x11
+#define LS_ENABLE               0x3D2
+#define LS_DISABLE              0x3D3
+#define LS_MODE                 0x3D8
+#define LS_MONSENSE             0x3DA
 // #define LV_PORT                 0x3E8
 // #define LV_PALETTE_0            0x00
 // #define LV_MODE_CONTROL         0x10
@@ -396,8 +398,8 @@ epoch_out(uint16_t addr, uint16_t val, void *priv)
             mem_mapping_disable(&epoch->vmap);
             // mem_mapping_enable(&epoch->paritymap);
             break;
-        case 0x3D8:
-            /* Bit 3: Font access in read, Bit 1: graphic mode, Bit 0: Font access in write */
+        case LS_MODE:
+            /* Bit 3: Video output enable, Bit 1: Graphic mode (switch 16 / 9 bit word in Font 16 system) */
             epoch->crtmode = val;
 #ifdef ENABLE_EPOCH_LOG
             // epoch_dumpvram(epoch);
@@ -515,7 +517,7 @@ epoch_in(uint16_t addr, void *priv)
         //     // epoch_iolog("epoch In %04X(%02X) %04X %04X:%04X\n", addr, epoch->attraddr, temp, cs >> 4, cpu_state.pc);
         //     epoch->attrff = 0; /* reset flipflop (VGA does not reset flipflop) */
         //     break;
-        case 0x3DA:
+        case LS_MONSENSE:
             temp = 0xff;
             if (!(epoch->crtmode & 0x08)) {/* The video out is active */
                 if(epoch->cgastat & 8)
@@ -525,7 +527,7 @@ epoch_in(uint16_t addr, void *priv)
             // temp &= 0xfe; /* color */
             break;
         }
-    if (addr != 0x3DA)
+    if (addr != LS_MONSENSE)
         epoch_iolog("%04X:%04X epoch In %04X %04X\n", cs >> 4, cpu_state.pc, addr, temp);
     return temp;
 }
@@ -1208,15 +1210,15 @@ epoch_vram_read(uint32_t addr, void *priv)
     return epoch->vram[addr];
 }
 
-static void
-epoch_vram_writeb(uint32_t addr, uint8_t val, void *priv)
-{
-    epoch_t *epoch = (epoch_t *) priv;
-//    epoch_log("%04X:%04X epoch_vwb: %x, val %x\n", cs >> 4, cpu_state.pc, addr, val);
-    cycles -= video_timing_write_b;
-    // return;
-//    epoch_vram_write(addr, val, epoch);
-}
+// static void
+// epoch_vram_writeb(uint32_t addr, uint8_t val, void *priv)
+// {
+//     epoch_t *epoch = (epoch_t *) priv;
+// //    epoch_log("%04X:%04X epoch_vwb: %x, val %x\n", cs >> 4, cpu_state.pc, addr, val);
+//     cycles -= video_timing_write_b;
+//     // return;
+// //    epoch_vram_write(addr, val, epoch);
+// }
 static void
 epoch_vram_writew(uint32_t addr, uint16_t val, void *priv)
 {
@@ -1310,15 +1312,15 @@ epoch_vram_writew(uint32_t addr, uint16_t val, void *priv)
     // epoch_log("%x %x\n", addr, addr + 1);
 }
 
-static uint8_t
-epoch_vram_readb(uint32_t addr, void *priv)
-{
-    epoch_t *epoch = (epoch_t *) priv;
-    cycles -= video_timing_read_b;
-    // return 0xff;
- //   epoch_log("%04X:%04X epoch_vrb: %x, val %x\n", cs >> 4, cpu_state.pc, addr, epoch_vram_read(addr, epoch));
-    // return epoch_vram_read(addr, epoch);
-}
+// static uint8_t
+// epoch_vram_readb(uint32_t addr, void *priv)
+// {
+//     epoch_t *epoch = (epoch_t *) priv;
+//     cycles -= video_timing_read_b;
+//     // return 0xff;
+//  //   epoch_log("%04X:%04X epoch_vrb: %x, val %x\n", cs >> 4, cpu_state.pc, addr, epoch_vram_read(addr, epoch));
+//     // return epoch_vram_read(addr, epoch);
+// }
 
 static uint16_t
 epoch_vram_readw(uint32_t addr, void *priv)
@@ -2320,8 +2322,8 @@ epoch_init(UNUSED(const device_t *info))
 
     mem_mapping_add(&epoch->cmap, 0xE0000, 0x1000, epoch_cram_readb, epoch_cram_readw, NULL,
         epoch_cram_writeb, epoch_cram_writew, NULL, NULL, MEM_MAPPING_EXTERNAL, epoch);
-    mem_mapping_add(&epoch->vmap, 0xA0000, 0x40000, epoch_vram_readb, epoch_vram_readw, NULL,
-        epoch_vram_writeb, epoch_vram_writew, NULL, NULL, MEM_MAPPING_EXTERNAL, epoch);
+    mem_mapping_add(&epoch->vmap, 0xA0000, 0x40000, NULL, epoch_vram_readw, NULL,
+        NULL, epoch_vram_writew, NULL, NULL, MEM_MAPPING_EXTERNAL, epoch);
     // mem_mapping_add(&epoch->fontcard.map, 0xF0000, 0xC000, epoch_font_readb, NULL, NULL,
     //     epoch_font_writeb, NULL, NULL, NULL, MEM_MAPPING_EXTERNAL, epoch);
 

From 4284f155747e944e902bc7be34ebfe6e7fab1617 Mon Sep 17 00:00:00 2001
From: Akamaki <97360908+akmed772@users.noreply.github.com>
Date: Fri, 20 Feb 2026 09:03:45 +0900
Subject: [PATCH 04/11] Keyboard: Fix a bug in IBM 5576-001 emulation

Fix a bug that the make code is sent when the 5576-001 emulation is enabled and the key is released.
---
 src/device/keyboard.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/src/device/keyboard.c b/src/device/keyboard.c
index e77a5fc1d..ea8bcc1e7 100644
--- a/src/device/keyboard.c
+++ b/src/device/keyboard.c
@@ -216,22 +216,24 @@ key_process(uint16_t scan, int down)
     */
     if (key5576mode) {
         int i = 0;
-        if (!down) {
-            /* Do and exit the 5576-001 emulation when a key is pressed other than trigger keys. */
-            if (scan != 0x1d && scan != 0x2a && scan != 0x138)
-            {
+        if (down) {
+            while (scconv55_8a[i].sc != 0) {
+                if (scconv55_8a[i].sc == scan) {
+                    while (scconv55_8a[i].mk[c] != 0)
+                        keyboard_send(scconv55_8a[i].mk[c++]);
+                }
+                i++;
+            }
+        }
+        /* Do and exit the 5576-001 emulation when a key is pressed other than trigger keys. */
+        if (scan != 0x1d && scan != 0x2a && scan != 0x138) {
+            if (!down) {
                 key5576mode = 0;
                 kbc_at_log("5576-001 key emulation disabled.\n");
             }
-        }
-        while (scconv55_8a[i].sc != 0)
-        {
-            if (scconv55_8a[i].sc == scan) {
-                while (scconv55_8a[i].mk[c] != 0)
-                    keyboard_send(scconv55_8a[i].mk[c++]);
-                return;
-            }
-            i++;
+            /* If the key is found in the table, the scancode has been sent.
+               Or else, do nothing. */
+            return;
         }
     }
 

From c1661b5a90121cb37952c29db6901c29c747fa8a Mon Sep 17 00:00:00 2001
From: Akamaki <97360908+akmed772@users.noreply.github.com>
Date: Fri, 20 Feb 2026 09:06:33 +0900
Subject: [PATCH 05/11] IBM 5550: Fix the screen res in graphic mode

---
 src/machine/m_xt_ibm5550.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/machine/m_xt_ibm5550.c b/src/machine/m_xt_ibm5550.c
index ff369dede..35edec8f3 100644
--- a/src/machine/m_xt_ibm5550.c
+++ b/src/machine/m_xt_ibm5550.c
@@ -305,7 +305,7 @@ The IBM 5550 has different IRQ assignments like the 6580 Displaywriter System.
 | 40000h        | 128 KB Expansion RAM Card                             | 
 | 60000h        | 128 KB Expansion RAM Card                             | 
 | 80000h        | 128 KB Expansion RAM Card                             | 
-| A0000h        | 256 KB Video RAM                                      | 
+| A0000h        | Video RAM (Font 16: 144 KB, Font 24: 256 KB)          | 
 | E0000h        | 4 KB Code/Attribute Buffer                            | 
 | E8000h        | ? KB Hard Disk Control Local Memory (not implemented) | 
 | F0000h        | Kanji Font Card (not implemented)                     | 
@@ -917,13 +917,15 @@ epoch_render_color_4bpp(epoch_t *epoch)
 /*
     INT 10h video modes supported in DOS K3.44.
     Mode        Type    Colors  Text    Base Address    PELs        Render
-    2           A/N     3       80 x 25 E0000h          1040 x 725  text
-    8           A/N/K   3       80 x 25 E0000h          1040 x 725  text
+    2           A/N     3       80 x 25 E0000h          1040 x 725* text
+    8           A/N/K   3       80 x 25 E0000h          1040 x 725* text
+    9           APA     2       80 x 25 A0000h          720 x 512   color_4bpp
     Ah          APA     2       78 x 25 A0000h          1024 x 768  color_4bpp
     Bh          APA     16      40 x 25 A0000h          360 x 512   n/a
     Ch          APA     16      80 x 25 A0000h          720 x 512   n/a
     Dh          APA     16      78 x 25 A0000h          1024 x 768  n/a
-    Eh          A/N/K   16      80 x 25 E0000h          1040 x 725  n/a
+    Eh          A/N/K   16      80 x 25 E0000h          1040 x 725* n/a
+                                        (* 720 x 525 in the Font 16 system.)
 */
 static void
 epoch_recalctimings(epoch_t *epoch)
@@ -978,8 +980,8 @@ epoch_recalctimings(epoch_t *epoch)
             epoch->hdisp *= 16;
             epoch->char_width = 16;
         } else {
-            epoch->hdisp *= 11;
-            epoch->char_width = 11;
+            epoch->hdisp *= 12;
+            epoch->char_width = 12;
         }
         /* PS/55 8-color */
         epoch_log("Set videomode to PS/55 4 bpp graphics.\n");

From 45c300a566b43af67a0da631bfc435d580532a46 Mon Sep 17 00:00:00 2001
From: Akamaki <97360908+akmed772@users.noreply.github.com>
Date: Fri, 20 Feb 2026 09:10:16 +0900
Subject: [PATCH 06/11] IBM 5550: Change method to store 9th bit into memory

---
 src/machine/m_xt_ibm5550.c | 33 ++++++++++++++++-----------------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/src/machine/m_xt_ibm5550.c b/src/machine/m_xt_ibm5550.c
index 35edec8f3..f13ccd6be 100644
--- a/src/machine/m_xt_ibm5550.c
+++ b/src/machine/m_xt_ibm5550.c
@@ -1236,7 +1236,7 @@ epoch_vram_writew(uint32_t addr, uint16_t val, void *priv)
     // uint8_t convert[8] = {4, 6, 8, 8, 5, 7, 8, 8};/* only odd (0) */
     // uint8_t convert[8] = {8, 4, 6, 8, 8, 5, 7, 8};/* none */
     // epoch_log("%04X:%04X epoch_vww: %x, val %x DS %x SI %x ES %x DI %x %x\n", cs >> 4, cpu_state.pc, addr, val,DS,SI,ES,DI, epoch->crtc[LC_INTERLACE_AND_SKEW]);
-    epoch_log("%04X:%04X epoch_vww: %x, val %x cm %x\n", cs >> 4, cpu_state.pc, addr, val, epoch->crtmode);
+    // epoch_log("%04X:%04X epoch_vww: %x, val %x cm %x\n", cs >> 4, cpu_state.pc, addr, val, epoch->crtmode);
     cycles -= video_timing_write_w;
     addr -= 0xA0000;
     // addr &= 0xfffffffe;
@@ -1291,21 +1291,21 @@ epoch_vram_writew(uint32_t addr, uint16_t val, void *priv)
         if (addr & 2)
             toaddr--;
         if (addr & 0x20000)
-            toaddr+=2;
-        toaddr &= 0xdffff;
+            toaddr += 2;
+        toaddr &= 0x1ffff;
 
         //addr >>= 1;
         
         epoch_vram_write(toaddr, val & 0xff, epoch);
         // epoch_log("%x %x ", toaddr, val);
         /* get 9th bit */
-        bitnum =  addr & 0x7;
+        bitnum =  toaddr & 0x7;
+        toaddr >>= 3;
+        toaddr += 0x20000; /* real: C0000h */
         val >>= 15;
         val <<= bitnum;
-        addr >>= 3;
-        addr += 0x20000; /* real: C0000h */
-        val |= epoch_vram_read(addr, epoch) & ~(1 << bitnum);/* mask to update one bit */
-        epoch_vram_write(addr, val, epoch);
+        val |= epoch_vram_read(toaddr, epoch) & ~(1 << bitnum);/* mask to update one bit */
+        epoch_vram_write(toaddr, val, epoch);
         // epoch_log("%x %x\n", addr, val);
     } else {/* is graphic mode */
         epoch_vram_write(addr, val & 0xff, epoch);
@@ -1332,8 +1332,7 @@ epoch_vram_readw(uint32_t addr, void *priv)
     // uint8_t convert[8] = {0, 4, 8, 8, 8, 8, 8, 8};/* all but pos+-1 */
     cycles -= video_timing_read_w;
     addr -= 0xA0000;
-   epoch_log("%04X:%04X epoch_vrw: %x cm %x\n", 
-    cs >> 4, cpu_state.pc, addr, epoch->crtmode);
+    // epoch_log("%04X:%04X epoch_vrw: %x cm %x\n", cs >> 4, cpu_state.pc, addr, epoch->crtmode);
     // addr &= 0xfffffffe;
     //read 0->0,1 2->2,3 4->4,5 6->6,7
     //read 0->0,2 2->1,3 4->4,6 6->5,7
@@ -1387,14 +1386,14 @@ epoch_vram_readw(uint32_t addr, void *priv)
         if (addr & 2)
             toaddr--;
         if (addr & 0x20000)
-            toaddr+=2;
-        toaddr &= 0xdffff;
+            toaddr += 2;
+        toaddr &= 0x1ffff;
         ret = epoch_vram_read(toaddr, epoch);
         /* get 9th bit */
-        bitnum =  addr & 0x7;
-        addr >>= 3;
-        addr += 0x20000; /* real: C0000h */
-        ret |= (epoch_vram_read(addr, epoch) << (8 + 7 - bitnum)) & 0x8000;
+        bitnum =  toaddr & 0x7;
+        toaddr >>= 3;
+        toaddr += 0x20000; /* real: C0000h */
+        ret |= (epoch_vram_read(toaddr, epoch) << (8 + 7 - bitnum)) & 0x8000;
         return ret;
         // return epoch_vram_read(addr, epoch) | (epoch_vram_read(addr + 1, epoch) << 8);
     } else {/* is graphic mode */
@@ -1806,7 +1805,7 @@ kbd_write(uint16_t port, uint8_t val, void *priv)
 
             timer_process();
             speaker_update();
-
+            // if(!speaker_enable && (val & 2)) epoch_log("Buz!\n");
             speaker_gated  = val & 2;
             speaker_enable = val & 2;
 

From 617be3b135e6a89a4f6c973aba14f16b745d1a03 Mon Sep 17 00:00:00 2001
From: Akamaki <97360908+akmed772@users.noreply.github.com>
Date: Fri, 20 Feb 2026 10:51:00 +0900
Subject: [PATCH 07/11] IBM 5550: Fix a bug in Font 16 drawing

---
 src/machine/m_xt_ibm5550.c | 78 +++++++++++++++++++++-----------------
 1 file changed, 44 insertions(+), 34 deletions(-)

diff --git a/src/machine/m_xt_ibm5550.c b/src/machine/m_xt_ibm5550.c
index f13ccd6be..2edb547a4 100644
--- a/src/machine/m_xt_ibm5550.c
+++ b/src/machine/m_xt_ibm5550.c
@@ -646,6 +646,18 @@ epoch_inw(uint16_t addr, void *priv)
     return temp;
 }
 
+static uint32_t
+getaddr_9bitword(int32_t addr)
+{
+            int32_t bit9addr = addr;
+            if (bit9addr & 2)
+                bit9addr--;
+            if (bit9addr & 0x20000)
+                bit9addr += 2;
+            bit9addr &= 0x1ffff;
+            return bit9addr;
+}
+
 /* Get font pattern in a line from video memory */
 static uint32_t
 getfont_ps55dbcs(int32_t code, int32_t line, void *priv)
@@ -667,19 +679,22 @@ getfont_ps55dbcs(int32_t code, int32_t line, void *priv)
             code++;
             font |= epoch->vram[code];
         } else { /* Font 16 (2 x 9 x 21) */
-            int bitnum = code & 0x7;
+            int32_t bit9addr = getaddr_9bitword(code);
+            int bitnum = bit9addr & 7;
+            bit9addr >>= 3;
+            bit9addr += 0x20000; /* real: C0000h */
             font = epoch->vram[code];
             font <<= 8;
-            font |= (epoch->vram[(code >> 3) + 0x20000 ] << (7 - bitnum)) & 0xff; /* get 9th bit */
-            // font &= 0xffffff80;
+            font |= (epoch->vram[bit9addr] << (7 - bitnum)) & 0x80; /* get 9th bit */
+            // font &= 0xff80;
             // font |= epoch->vram[code + line * 4 + 1];
             font <<= 8;
             code++;
             font |= epoch->vram[code];
             font <<= 8;
             bitnum = code & 0x7;
-            font |= (epoch->vram[(code >> 3) + 0x20000 ] << (7 - bitnum)) & 0xff; /* get 9th bit */
-            font &= 0xff80ff80;
+            font |= (epoch->vram[bit9addr] << (7 - bitnum)) & 0x80; /* get 9th bit */
+            // font &= 0xff80ff80;
             // font |= epoch->vram[code + line * 4 + 3];
         }
     } else
@@ -801,15 +816,17 @@ epoch_render_text(epoch_t *epoch)
                         font <<= 8;
                         font |= epoch->vram[fontbase + chr * 0x80 + epoch->scanline * 4 + 3];
                     } else {
-                        int bitnum;
-                        fontbase = (fontbase & 0x1ffff) + chr * 0x80 + epoch->scanline * 4;
-                        bitnum = fontbase & 0x7;
+                        uint32_t bitnum, bit9addr;
+                        fontbase += chr * 0x80 + epoch->scanline * 4;
+                        bit9addr = getaddr_9bitword(fontbase);
+                        bitnum   = bit9addr & 7;
+                        bit9addr >>= 3;
+                        bit9addr += 0x20000; /* real: C0000h */
+
+                        fontbase &= 0x1ffff;
                         font = epoch->vram[fontbase + 2]; /* w9xh21 font */
                         font <<= 8;
-                        // font |= epoch->vram[fontbase + chr * 0x80 + epoch->scanline * 4 + 3];
-                        fontbase >>= 3;
-                        fontbase += 0x20000; /* real: C0000h */
-                        font |= epoch->vram[fontbase] << (8 + 7 - bitnum);
+                        font |= (epoch->vram[bit9addr] << (7 - bitnum)) & 0x80;
                         // if(chr!=0x20) epoch_log("faddr: %x, scline: %x, chr: %x, font: %x    ", fontbase + chr * 0x80 + epoch->scanline * 4, epoch->scanline, chr, font);
                     }
                     // if(chr!=0x20) epoch_log("memaddr: %x, scanline: %x, chr: %x, font: %x    ", epoch->memaddr, epoch->scanline, chr, font);
@@ -1287,31 +1304,27 @@ epoch_vram_writew(uint32_t addr, uint16_t val, void *priv)
 
         /* rw one word with 9 bits */
         /* virtual: 20000h (0010b, 0011b) -> real: 00001h (0000b, 0001b) */
-        toaddr = addr;
-        if (addr & 2)
-            toaddr--;
-        if (addr & 0x20000)
-            toaddr += 2;
-        toaddr &= 0x1ffff;
-
-        //addr >>= 1;
         
+        toaddr = getaddr_9bitword(addr);
+        bitnum   = toaddr & 7;
         epoch_vram_write(toaddr, val & 0xff, epoch);
-        // epoch_log("%x %x ", toaddr, val);
+        // epoch_log("%x %x\n", toaddr, val);
         /* get 9th bit */
-        bitnum =  toaddr & 0x7;
         toaddr >>= 3;
         toaddr += 0x20000; /* real: C0000h */
         val >>= 15;
+        // epoch_log("%x %x ", toaddr, val);
         val <<= bitnum;
-        val |= epoch_vram_read(toaddr, epoch) & ~(1 << bitnum);/* mask to update one bit */
+        // epoch_log("%x ", val);
+        val |= (epoch_vram_read(toaddr, epoch) & (~(1 << bitnum)));/* mask to update one bit */
         epoch_vram_write(toaddr, val, epoch);
+        // epoch_log("%x %x\n", toaddr, val);
         // epoch_log("%x %x\n", addr, val);
     } else {/* is graphic mode */
         epoch_vram_write(addr, val & 0xff, epoch);
         epoch_vram_write(addr + 1, val >> 8, epoch);
     }
-    // epoch_log("%x %x\n", addr, addr + 1);
+    // epoch_log("%x %x\n", addr, val);
 }
 
 // static uint8_t
@@ -1382,15 +1395,10 @@ epoch_vram_readw(uint32_t addr, void *priv)
         
         /* rw one word with 9 bits */
         /* virtual: 20000h (0010b, 0011b) -> real: 00001h (0000b, 0001b) */
-        toaddr = addr; /* 1101 */
-        if (addr & 2)
-            toaddr--;
-        if (addr & 0x20000)
-            toaddr += 2;
-        toaddr &= 0x1ffff;
+        toaddr = getaddr_9bitword(addr);
+        bitnum   = toaddr & 7;
         ret = epoch_vram_read(toaddr, epoch);
         /* get 9th bit */
-        bitnum =  toaddr & 0x7;
         toaddr >>= 3;
         toaddr += 0x20000; /* real: C0000h */
         ret |= (epoch_vram_read(toaddr, epoch) << (8 + 7 - bitnum)) & 0x8000;
@@ -2148,11 +2156,11 @@ epoch_nvr_reset(nvr_t *nvr)
 }
 
 static void
-epoch_nvr_init(epoch_t *epoch, int size)
+epoch_nvr_init(epoch_t *epoch)
 {
     nvr_t* nvr = &epoch->nvr;
     /* This is machine specific. */
-    nvr->size = size;
+    nvr->size = 17;
     nvr->irq  = -1;
     /* Set up any local handlers here. */
     nvr->reset = epoch_nvr_reset;
@@ -2315,6 +2323,8 @@ epoch_init(UNUSED(const device_t *info))
     changeframecount = 3;
 
     epoch->vram              = calloc(1, 256* 1024);
+    // for(int i=0;i<256*1024;i++) /* for debug */
+    //     epoch->vram[i] = 0xff;
     epoch->cram              = calloc(1, 4 * 1024);
     // epoch->fontcard.rom      = calloc(1, EPOCH_FONTROM_SIZE);
     // epoch_video_load_font("roms/machines/ibm5550/GEN1FONT.BIN", epoch);
@@ -2347,7 +2357,7 @@ epoch_init(UNUSED(const device_t *info))
     
     timer_add(&epoch->timer, epoch_poll, epoch, 1);
 
-    epoch_nvr_init(epoch, 17);
+    epoch_nvr_init(epoch);
 
     epoch->font24 = device_get_config_int("model");
 

From c03a4e91c945fe1745d958e7d44e6074c276644a Mon Sep 17 00:00:00 2001
From: Akamaki <97360908+akmed772@users.noreply.github.com>
Date: Fri, 20 Feb 2026 23:36:08 +0900
Subject: [PATCH 08/11] IBM 5550: Add cursor blinking

Added cursor blinking controlled by CRTC (HD46505).
---
 src/machine/m_xt_ibm5550.c | 20 +++++++++++++++++---
 src/video/vid_ps55da2.c    |  2 +-
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/src/machine/m_xt_ibm5550.c b/src/machine/m_xt_ibm5550.c
index 2edb547a4..ccc55578b 100644
--- a/src/machine/m_xt_ibm5550.c
+++ b/src/machine/m_xt_ibm5550.c
@@ -862,7 +862,7 @@ epoch_render_text(epoch_t *epoch)
             }
             /* Drawing text cursor */
             drawcursor = ((epoch->memaddr == epoch->cursoraddr) && epoch->cursorvisible && epoch->cursoron);
-            if (drawcursor && epoch->scanline >= epoch->crtc[LC_CURSOR_ROW_START] && epoch->scanline <= epoch->crtc[LC_CURSOR_ROW_END]) {
+            if (drawcursor) {
                 // int cursorwidth = (epoch->crtc[LC_COMPATIBILITY] & 0x20 ? 26 : 13);
                 int cursorwidth = epoch->char_width;
                 int cursorcolor = 2; /* Choose color 2 if mode 8 */
@@ -1140,11 +1140,25 @@ epoch_poll(void *priv)
                 // if (epoch->attrc[LV_CURSOR_CONTROL] & 0x01) /* cursor blinking */
                 // {
                     // epoch->cursoron = (epoch->blink | 1) & epoch->blinkconf;
-                    epoch->cursoron = 1;
+                    // epoch->cursoron = 1;
                 // } else {
                 //     epoch->cursoron = 0;
                 // }
-                if (!(epoch->blink & (0x10 - 1))) /* force redrawing for cursor and blink attribute */
+                switch (epoch->crtc[LC_CURSOR_ROW_START] & 0x60) {
+                    case 0x20:
+                        epoch->cursoron = 0;
+                        break;
+                    case 0x60:
+                        epoch->cursoron = epoch->blink & 0x10;
+                        break;
+                    case 0x40:
+                        epoch->cursoron = epoch->blink & 0x08;
+                        break;
+                    default:
+                        epoch->cursoron = 1;
+                        break;
+                }
+                if (!(epoch->blink & (0x08 - 2))) /* force redrawing for cursor and blink attribute */
                     epoch->fullchange = changeframecount;
             }
             epoch->blink++;
diff --git a/src/video/vid_ps55da2.c b/src/video/vid_ps55da2.c
index a1d7fe25f..9dffcdf97 100644
--- a/src/video/vid_ps55da2.c
+++ b/src/video/vid_ps55da2.c
@@ -2055,7 +2055,7 @@ da2_render_text(da2_t *da2)
             }
             /* Drawing text cursor */
             drawcursor = ((da2->memaddr == da2->cursoraddr) && da2->cursorvisible && da2->cursoron);
-            if (drawcursor && da2->scanline >= da2->crtc[LC_CURSOR_ROW_START] && da2->scanline <= da2->crtc[LC_CURSOR_ROW_END]) {
+            if (drawcursor) {
                 int cursorwidth = (da2->crtc[LC_COMPATIBILITY] & 0x20 ? 26 : 13);
                 int cursorcolor = (colormode) ? IRGBtoBGRI(da2->attrc[LV_CURSOR_COLOR]) : 2; /* Choose color 2 if mode 8 */
                 fg              = (colormode) ? getPS55ForeColor(attr, da2) : ((attr & 0x08) ? 3 : 2);

From 894e4bb0cf08456d3221b47b67744dfce04c7ed9 Mon Sep 17 00:00:00 2001
From: Akamaki <97360908+akmed772@users.noreply.github.com>
Date: Sat, 21 Feb 2026 02:25:07 +0900
Subject: [PATCH 09/11] IBM 5550: Set pixel clock for Font 16

---
 src/machine/m_xt_ibm5550.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/src/machine/m_xt_ibm5550.c b/src/machine/m_xt_ibm5550.c
index ccc55578b..aefbf0193 100644
--- a/src/machine/m_xt_ibm5550.c
+++ b/src/machine/m_xt_ibm5550.c
@@ -73,7 +73,8 @@
 #define EPOCH_MASK_CRAM            0xfff         /* 0xFFF */
 #define EPOCH_MASK_VRAM            0x3ffff       /* 0xFFFFF */
 // #define EPOCH_MASK_VRAMPLANE       0x1ffff       /* 0x1FFFF */
-#define EPOCH_PIXELCLOCK           40000000.0    /* 40 MHz interlaced */
+#define EPOCH_PIXELCLOCK24         40000000.0    /* 40 MHz interlaced */
+#define EPOCH_PIXELCLOCK16         20000000.0    /* 20 MHz interlaced (not confirmed) */
 #define EPOCH_CONFIG_MONO16 0 /* Model 5551-Axx (Font 16, monochrome) */
 #define EPOCH_CONFIG_MONO24 1 /* Model 5551-Bxx (Font 24, monochrome) */
 
@@ -241,6 +242,7 @@ typedef struct epoch_t {
     int      scrollcache;
     int      char_width;
     int      font24;
+    double   pixelclock;
 
     int firstline, lastline;
     int firstline_draw, lastline_draw;
@@ -1088,7 +1090,7 @@ epoch_poll(void *priv)
                 video_wait_for_buffer();
             }
 
-            if((epoch->displine ^ !epoch->oddeven) & 1)
+            if ((epoch->displine ^ !epoch->oddeven) & 1)
                 epoch->render(epoch);
 
             if (epoch->lastline < epoch->displine)
@@ -1199,8 +1201,8 @@ epoch_poll(void *priv)
 
             epoch->vslines     = 0;
 
-                epoch->memaddr
-                    = epoch->memaddr_backup = epoch->memaddr_latch << 1;
+            epoch->memaddr
+                = epoch->memaddr_backup = epoch->memaddr_latch << 1;
             epoch->cursoraddr = ((epoch->crtc[LC_CURSOR_LOC_HIGH] << 8) | epoch->crtc[LC_CURSOR_LOC_LOWJ]) + epoch->ca_adj;
             epoch->cursoraddr <<= 1;
 
@@ -1431,7 +1433,7 @@ epoch_cram_write(uint32_t addr, uint8_t val, void *priv)
     // if ((addr & ~0xfff) != 0xE0000) return;
     addr &= EPOCH_MASK_CRAM;
     epoch->cram[addr] = val;
-    epoch->fullchange = changeframecount;;
+    epoch->fullchange = changeframecount;
     // epoch_log("cw %04X:%04X %04X %02X\n", cs >> 4, cpu_state.pc, addr, val);
 }
 static void
@@ -2328,6 +2330,8 @@ static void *
 epoch_init(UNUSED(const device_t *info))
 {
     epoch_t *epoch  = calloc(1, sizeof(epoch_t));
+    epoch->font24 = device_get_config_int("model");
+
     video_inform(VIDEO_FLAG_TYPE_NONE, &timing_epoch_vid);
     video_update_timing();
 
@@ -2335,6 +2339,10 @@ epoch_init(UNUSED(const device_t *info))
     epoch->dispofftime       = 1000ull << 32;
     // epoch->changedvram       = calloc(1,  (EPOCH_MASK_VRAMPLANE + 1) >> 9); /* XX000h */
     changeframecount = 3;
+    if (epoch->font24)
+        epoch->pixelclock = EPOCH_PIXELCLOCK24;
+    else
+        epoch->pixelclock = EPOCH_PIXELCLOCK16;
 
     epoch->vram              = calloc(1, 256* 1024);
     // for(int i=0;i<256*1024;i++) /* for debug */
@@ -2343,7 +2351,7 @@ epoch_init(UNUSED(const device_t *info))
     // epoch->fontcard.rom      = calloc(1, EPOCH_FONTROM_SIZE);
     // epoch_video_load_font("roms/machines/ibm5550/GEN1FONT.BIN", epoch);
 
-    epoch->epochconst = (uint64_t) ((cpuclock / EPOCH_PIXELCLOCK) * (double) (1ull << 32));
+    epoch->epochconst = (uint64_t) ((cpuclock / epoch->pixelclock) * (double) (1ull << 32));
 
     mem_mapping_add(&epoch->cmap, 0xE0000, 0x1000, epoch_cram_readb, epoch_cram_readw, NULL,
         epoch_cram_writeb, epoch_cram_writew, NULL, NULL, MEM_MAPPING_EXTERNAL, epoch);
@@ -2373,8 +2381,6 @@ epoch_init(UNUSED(const device_t *info))
 
     epoch_nvr_init(epoch);
 
-    epoch->font24 = device_get_config_int("model");
-
     return epoch;
 }
 
@@ -2441,7 +2447,7 @@ static void
 epoch_speed_changed(void *priv)
 {
     epoch_t *epoch    = (epoch_t *) priv;
-    epoch->epochconst = (uint64_t) ((cpuclock / EPOCH_PIXELCLOCK) * (double) (1ull << 32));
+    epoch->epochconst = (uint64_t) ((cpuclock / epoch->pixelclock) * (double) (1ull << 32));
     epoch_recalctimings(epoch);
 }
 

From 3a199fb8cb83d4540d985e677d0431208f398ec8 Mon Sep 17 00:00:00 2001
From: Akamaki <97360908+akmed772@users.noreply.github.com>
Date: Sat, 21 Feb 2026 02:26:54 +0900
Subject: [PATCH 10/11] PS55DA2: Change to interlaced screen update

---
 src/video/vid_ps55da2.c | 62 ++++++++++++++++++++++++-----------------
 1 file changed, 37 insertions(+), 25 deletions(-)

diff --git a/src/video/vid_ps55da2.c b/src/video/vid_ps55da2.c
index 9dffcdf97..0bd5035b0 100644
--- a/src/video/vid_ps55da2.c
+++ b/src/video/vid_ps55da2.c
@@ -64,7 +64,7 @@
 #define DA2_MASK_GAIJIRAM        0x3ffff       /* 0x3FFFF */
 #define DA2_MASK_VRAM            0xfffff       /* 0xFFFFF */
 #define DA2_MASK_VRAMPLANE       0x1ffff       /* 0x1FFFF */
-#define DA2_PIXELCLOCK           29000000.0    /* 58 MHz interlaced */
+#define DA2_PIXELCLOCK           58000000.0    /* 58 MHz interlaced */
 #define DA2_BLT_MEMSIZE          0x10
 #define DA2_BLT_REGSIZE          0x40
 #define DA2_DEBUG_BLTLOG_SIZE    (DA2_BLT_REGSIZE + 1)
@@ -368,6 +368,7 @@ typedef struct da2_t {
     int firstline, lastline;
     int firstline_draw, lastline_draw;
     int displine;
+    int oddeven;
 
     /* Attribute Buffer E0000-E0FFFh (4 KB) */
     uint8_t *cram;
@@ -441,6 +442,9 @@ typedef struct da2_t {
     int old_pos2;
 } da2_t;
 
+static video_timings_t timing_da2_mca = 
+{ .type = VIDEO_MCA, .write_b = 4, .write_w = 4, .write_l =  10, .read_b = 4, .read_w = 4, .read_l = 10 };
+
 static void     da2_recalctimings(da2_t *da2);
 static void     da2_mmio_gc_writeW(uint32_t addr, uint16_t val, void *p);
 static void     da2_bitblt_exec(void *p);
@@ -515,7 +519,7 @@ da2_WritePlaneDataWithBitmask(uint32_t destaddr, const uint16_t mask, pixel32 *s
     uint32_t writepx[8];
     destaddr &= 0xfffffffe; /* align to word address to work bit shift correctly */
     // da2_log("DA2_WPDWB addr %x mask %x rop %x shift %d\n", destaddr, mask, da2->bitblt.raster_op, da2->bitblt.bitshift_destr);
-    da2->changedvram[(DA2_MASK_VRAMPLANE & destaddr) >> 9]       = changeframecount;
+    da2->changedvram[(DA2_MASK_VRAMPLANE & destaddr) >> 9]       = 3;
     destaddr <<= 3;
     /* read destination data with big endian order */
     for (uint8_t i = 0; i < 8; i++)
@@ -1245,7 +1249,7 @@ da2_out(uint16_t addr, uint16_t val, void *priv)
         case 0x3C9: /* Data */
             // da2_iolog("DA2 Out addr %03X idx %d:%d val %02X %04X:%04X esdi %04X:%04X\n", addr, da2->dac_write, da2->dac_pos, val, cs >> 4, cpu_state.pc, ES, DI);
             da2->dac_status = 0;
-            da2->fullchange = changeframecount;
+            da2->fullchange = 3;
             switch (da2->dac_pos) {
                 case 0:
                     da2->dac_r = val;
@@ -1283,7 +1287,7 @@ da2_out(uint16_t addr, uint16_t val, void *priv)
                 if (da2->ioctladdr == LS_RESET && val & 0x01) /* Reset register */
                     da2_reset_ioctl(da2);
                 else if (da2->ioctladdr == LS_MODE && ((oldval ^ val) & 0x03)) { /* Mode register */
-                    da2->fullchange = changeframecount;
+                    da2->fullchange = 3;
                     da2_recalctimings(da2);
                     da2_updatevidselector(da2);
                 }
@@ -1372,7 +1376,7 @@ da2_out(uint16_t addr, uint16_t val, void *priv)
                 case LC_START_V_DISPLAY_ENAB:
                 case LC_VIEWPORT_SELECT:
                 case LC_VIEWPORT_PRIORITY:
-                    da2->fullchange = changeframecount;
+                    da2->fullchange = 3;
                     da2_recalctimings(da2);
                     break;
                 default:
@@ -1391,13 +1395,13 @@ da2_out(uint16_t addr, uint16_t val, void *priv)
                 // da2_iolog("set attraddr: %X\n", da2->attraddr);
             } else {
                 if ((da2->attraddr == LV_PANNING) && (da2->attrc[LV_PANNING] != val))
-                    da2->fullchange = changeframecount;
+                    da2->fullchange = 3;
                 if (da2->attrc[da2->attraddr & 0x3f] != val)
                     da2_iolog("attr changed %x: %x -> %x\n", da2->attraddr & 0x3f, da2->attrc[da2->attraddr & 0x3f], val);
                 da2->attrc[da2->attraddr & 0x3f] = val;
                 // da2_iolog("set attrc %x: %x\n", da2->attraddr & 31, val);
                 if (da2->attraddr < 16)
-                    da2->fullchange = changeframecount;
+                    da2->fullchange = 3;
                 if (da2->attraddr == LV_MODE_CONTROL || da2->attraddr < 0x10) {
                     for (uint8_t c = 0; c < 16; c++) {
                         // if (da2->attrc[LV_MODE_CONTROL] & 0x80) da2->egapal[c] = (da2->attrc[c] & 0xf) | ((da2->attrc[0x14] & 0xf) << 4);
@@ -1411,7 +1415,7 @@ da2_out(uint16_t addr, uint16_t val, void *priv)
                 switch (da2->attraddr) {
                     case LV_COLOR_PLANE_ENAB:
                         if ((val & 0xff) != da2->plane_mask)
-                            da2->fullchange = changeframecount;
+                            da2->fullchange = 3;
                         da2->plane_mask = val & 0xff;
                         break;
                     case LV_CURSOR_CONTROL:
@@ -2743,7 +2747,7 @@ da2_mmio_write(uint32_t addr, uint8_t val, void *priv)
         //}
 #endif
         cycles -= video_timing_write_b;
-        da2->changedvram[addr >> 9] = changeframecount;/* 0x1FFFF -> 0x1F */
+        da2->changedvram[addr >> 9] = 3;/* 0x1FFFF -> 0x1F */
         addr <<= 3;
 
         for (uint8_t i = 0; i < 8; i++)
@@ -2804,7 +2808,7 @@ da2_mmio_write(uint32_t addr, uint8_t val, void *priv)
     } else { /*  mode 3h text */
         cycles -= video_timing_write_b;
         da2_vram_w(addr, val, da2);
-        da2->fullchange = 2;
+        da2->fullchange = 3;
     }
 }
 static uint16_t
@@ -2843,7 +2847,7 @@ da2_mmio_gc_writeW(uint32_t addr, uint16_t val, void *priv)
     // da2_log("da2_gcW m%d a%x d%x\n", da2->writemode, addr, val);
     // da2_log("da2_gcW %05X %02X %04X:%04X esdi %04X:%04X dssi %04X:%04X\n", addr, val, cs >> 4, cpu_state.pc, ES, DI, DS, SI);
 
-    da2->changedvram[addr >> 9]       = changeframecount;
+    da2->changedvram[addr >> 9]       = 3;
     addr <<= 3;
 
     for (uint8_t i = 0; i < 8; i++)
@@ -2942,7 +2946,7 @@ da2_code_write(uint32_t addr, uint8_t val, void *priv)
     // if ((addr & ~0xfff) != 0xE0000) return;
     addr &= DA2_MASK_CRAM;
     da2->cram[addr] = val;
-    da2->fullchange = 2;
+    da2->fullchange = 3;
 }
 static void
 da2_code_writeb(uint32_t addr, uint8_t val, void *priv)
@@ -2987,7 +2991,7 @@ da2_code_readw(uint32_t addr, void *priv)
 }
 
 static void
-da2_doblit(int y1, int y2, int wx, int wy, da2_t *da2)
+da2_doblit(int wx, int wy, da2_t *da2)
 {
     if (wx != xsize || wy != ysize) {
         xsize = wx;
@@ -3026,14 +3030,14 @@ da2_poll(void *priv)
                 video_wait_for_buffer();
             }
 
-            if (!da2->override)
+            if (!da2->override && ((da2->displine ^ !da2->oddeven) & 1))
                 da2->render(da2);
 
             if (da2->lastline < da2->displine)
                 da2->lastline = da2->displine;
         }
-
-        // da2_log("%03i %06X %06X\n", da2->displine, da2->memaddr,da2->vram_display_mask);
+        // if(da2->fullchange)
+        //     pclog("%03i %05X %d %d\n", da2->displine, da2->memaddr, ((da2->displine ^ !da2->oddeven) & 1), da2->fullchange);
         da2->displine++;
         if ((da2->cgastat & 8) && ((da2->displine & 0xf) == (da2->crtc[LC_VERTICAL_SYNC_END] & 0xf)) && da2->vslines) {
             // da2_log("Vsync off at line %i\n",displine);
@@ -3085,14 +3089,13 @@ da2_poll(void *priv)
             // if (da2->crtc[10] & 0x20) da2->cursoron = 0;
             // else da2->cursoron = da2->blink & 16;
             if (da2->ioctl[LS_MODE] & 1) {                /* in text mode */
-                if (da2->attrc[LV_CURSOR_CONTROL] & 0x01) /* cursor blinking */
-                {
+                if (da2->attrc[LV_CURSOR_CONTROL] & 0x01) {/* cursor blinking */
                     da2->cursoron = (da2->blink | 1) & da2->blinkconf;
                 } else {
                     da2->cursoron = 0;
                 }
-                if (!(da2->blink & (0x10 - 1))) /* force redrawing for cursor and blink attribute */
-                    da2->fullchange = 2;
+                if (!(da2->blink & (0x08 - 1))) /* force redrawing for cursor and blink attribute */
+                    da2->fullchange = 3;
             }
             da2->blink++;
 
@@ -3103,6 +3106,7 @@ da2_poll(void *priv)
             // memset(changedvram,0,2048);  del
             if (da2->fullchange) {
                 da2->fullchange--;
+                // pclog("fc %d %d\n",da2->fullchange,da2->oddeven);
             }
         }
         if (da2->vc == da2->vsyncstart) {
@@ -3112,10 +3116,15 @@ da2_poll(void *priv)
             da2->cgastat |= 8;
             x = da2->hdisp;
 
+            if (!da2->oddeven)
+                da2->lastline++;
+            if (da2->oddeven)
+                da2->firstline--;
+
             wx = x;
             wy = da2->lastline - da2->firstline;
 
-            da2_doblit(da2->firstline_draw, da2->lastline_draw + 1, wx, wy, da2);
+            da2_doblit(wx, wy, da2);
 
             da2->firstline = 2000;
             da2->lastline  = 0;
@@ -3123,7 +3132,8 @@ da2_poll(void *priv)
             da2->firstline_draw = 2000;
             da2->lastline_draw  = 0;
 
-            changeframecount = 2;
+            da2->oddeven ^= 1;
+
             da2->vslines     = 0;
 
             da2->memaddr
@@ -3137,7 +3147,7 @@ da2_poll(void *priv)
             // da2_log("VC vtotal\n");
             // printf("Frame over at line %i %i  %i %i\n",displine,vc,da2_vsyncstart,da2_dispend);
             da2->vc          = 0;
-            da2->scanline          = da2->crtc[LC_PRESET_ROW_SCANJ] & 0x1f;
+            da2->scanline    = da2->crtc[LC_PRESET_ROW_SCANJ] & 0x1f;
             da2->dispon      = 1;
             da2->displine    = 0;
             da2->scrollcache = da2->attrc[LV_PANNING] & 7;
@@ -3229,7 +3239,8 @@ da2_reset(void *priv)
     da2->attrc[LV_CURSOR_COLOR]    = 0x0f;                   /* cursor color */
     da2->crtc[LC_HORIZONTAL_TOTAL] = 63;                     /* Horizontal Total */
     da2->crtc[LC_VERTICAL_TOTALJ]  = 255;                    /* Vertical Total (These two must be set before the timer starts.) */
-    da2->memaddr_latch                  = 0;
+    da2->memaddr_latch             = 0;
+    da2->oddeven                   = 0;
     da2->attrc[LV_CURSOR_CONTROL]  = 0x13; /* cursor options */
     da2->attr_palette_enable       = 0;    /* disable attribute generator */
 
@@ -3278,6 +3289,7 @@ da2_init(UNUSED(const device_t *info))
 
     mca_add(da2_mca_read, da2_mca_write, da2_mca_feedb, da2_mca_reset, da2);
     da2->da2const = (uint64_t) ((cpuclock / DA2_PIXELCLOCK) * (double) (1ull << 32));
+    video_inform(VIDEO_FLAG_TYPE_SPECIAL, &timing_da2_mca);
     memset(da2->bitblt.payload, 0x00, DA2_BLT_MEMSIZE);
     memset(da2->bitblt.reg, 0xfe, DA2_BLT_REGSIZE * sizeof(uint32_t)); /* clear memory */
 #ifdef ENABLE_DA2_DEBUGBLT
@@ -3432,7 +3444,7 @@ static void
 da2_force_redraw(void *priv)
 {
     da2_t *da2      = (da2_t *) priv;
-    da2->fullchange = changeframecount;
+    da2->fullchange = 3;
 }
 
 static const device_config_t da2_configuration[] = {

From dad8edd32e89094d85a8ca7533dcae0aa222b72f Mon Sep 17 00:00:00 2001
From: Akamaki <97360908+akmed772@users.noreply.github.com>
Date: Sat, 21 Feb 2026 02:40:26 +0900
Subject: [PATCH 11/11] cleanup (m_xt_ibm5550.c)

---
 src/machine/m_xt_ibm5550.c | 169 ++++---------------------------------
 1 file changed, 17 insertions(+), 152 deletions(-)

diff --git a/src/machine/m_xt_ibm5550.c b/src/machine/m_xt_ibm5550.c
index aefbf0193..00f203f1a 100644
--- a/src/machine/m_xt_ibm5550.c
+++ b/src/machine/m_xt_ibm5550.c
@@ -18,7 +18,7 @@
  *          These first-gen models have 1-3 DSQD diskette drives.
  *          You need select "Type: 5.25" 720k" in the Settings dialog - Floppy & CD-ROM drives.
  * 
- *          Currently, this module only support the model B configuration without hard disk.
+ *          Currently, this module supports model A and B configurations without hard disk.
  * 
  * Authors: Akamaki.
  *
@@ -133,12 +133,12 @@
 // #define LV_OUTPUT               0x3E
 // #define LV_COMPATIBILITY        0x3F
 
-#define TIMER_CTR_0 0 //DMA
-#define TIMER_CTR_1 1 //8253 timer
-#define TIMER_CTR_2 2 //Speaker
+#define TIMER_CTR_0 0 /* DMA */
+#define TIMER_CTR_1 1 /* PIT */
+#define TIMER_CTR_2 2 /* Speaker */
 
-#define EPOCH_IRQ3_BIT (1 << 3) //Keyboard
-#define EPOCH_IRQ6_BIT (1 << 6) //Timer
+#define EPOCH_IRQ3_BIT (1 << 3) /* Keyboard */
+#define EPOCH_IRQ6_BIT (1 << 6) /* PIT */
 
 enum epoch_nvr_ADDR {
     epoch_nvr_SECOND1,
@@ -161,7 +161,7 @@ enum epoch_nvr_ADDR {
 };
 
 #ifndef RELEASE_BUILD
-#define ENABLE_EPOCH_LOG 1
+//#define ENABLE_EPOCH_LOG 1
 #endif
 
 #ifdef ENABLE_EPOCH_LOG
@@ -381,7 +381,7 @@ epoch_out(uint16_t addr, uint16_t val, void *priv)
                 case LC_MAXIMUM_SCAN_LINE:
                 case LC_START_ADDRESS_HIGH:
                 case LC_START_ADDRESS_LOW:
-                    epoch->fullchange = changeframecount;
+                    epoch->fullchange = 3;
                     epoch_recalctimings(epoch);
                     break;
                 default:
@@ -648,6 +648,7 @@ epoch_inw(uint16_t addr, void *priv)
     return temp;
 }
 
+/* Return a memory address for 9-bit word access */
 static uint32_t
 getaddr_9bitword(int32_t addr)
 {
@@ -1139,13 +1140,6 @@ epoch_poll(void *priv)
         if (epoch->vc == epoch->dispend) {
             epoch->dispon = 0;
             if (!(epoch->crtmode & 0x02)) {                /* in text mode */
-                // if (epoch->attrc[LV_CURSOR_CONTROL] & 0x01) /* cursor blinking */
-                // {
-                    // epoch->cursoron = (epoch->blink | 1) & epoch->blinkconf;
-                    // epoch->cursoron = 1;
-                // } else {
-                //     epoch->cursoron = 0;
-                // }
                 switch (epoch->crtc[LC_CURSOR_ROW_START] & 0x60) {
                     case 0x20:
                         epoch->cursoron = 0;
@@ -1161,7 +1155,7 @@ epoch_poll(void *priv)
                         break;
                 }
                 if (!(epoch->blink & (0x08 - 2))) /* force redrawing for cursor and blink attribute */
-                    epoch->fullchange = changeframecount;
+                    epoch->fullchange = 3;
             }
             epoch->blink++;
 
@@ -1227,112 +1221,44 @@ static void
 epoch_vram_write(uint32_t addr, uint8_t val, void *priv)
 {
     epoch_t *epoch = (epoch_t *) priv;
-    // if ((addr & ~0xfff) != 0xE0000) return;
     // epoch_log("epoch_vw: %x %x\n", addr, val);
     addr &= EPOCH_MASK_VRAM;
     epoch->vram[addr] = val;
-    epoch->fullchange = changeframecount;
-    // if(val == 0x66)
-    //         epoch_log("66 %04X:%04X %04X:%04X>%04X:%04X\n", cs >> 4, cpu_state.pc, DS, SI,ES,DI);
+    epoch->fullchange = 3;
 }
 static uint8_t
 epoch_vram_read(uint32_t addr, void *priv)
 {
     epoch_t *epoch = (epoch_t *) priv;
-    // if ((addr & ~epoch_MASK_CRAM) != 0xE0000)
-    //     return epoch_INVALIDACCESS8;
     addr &= EPOCH_MASK_VRAM;
     return epoch->vram[addr];
 }
 
-// static void
-// epoch_vram_writeb(uint32_t addr, uint8_t val, void *priv)
-// {
-//     epoch_t *epoch = (epoch_t *) priv;
-// //    epoch_log("%04X:%04X epoch_vwb: %x, val %x\n", cs >> 4, cpu_state.pc, addr, val);
-//     cycles -= video_timing_write_b;
-//     // return;
-// //    epoch_vram_write(addr, val, epoch);
-// }
 static void
 epoch_vram_writew(uint32_t addr, uint16_t val, void *priv)
 {
     epoch_t *epoch = (epoch_t *) priv;
-    // uint8_t convert[8] = {0, 2, 8, 8, 1, 3, 8, 8};/* only even chars */
-    //uint8_t convert[8] = {8, 8, 0, 2, 8, 8, 1, 3};/* only even chars */
-    // uint8_t convert[8] = {0, 1, 2, 3, 4, 5, 6, 7};/* all but alt */
-    // uint8_t convert[8] = {0, 1, 2, 3, 8, 8, 8, 8};/* even alt */
-    // uint8_t convert[8] = {8, 8, 8, 8, 0, 1, 2, 3};/* even alt */
-    // uint8_t convert[8] = {0, 4, 1, 5, 2, 6, 3, 7};/* all but pos+-1 */
-    // uint8_t convert[8] = {8, 8, 4, 6, 8, 8, 5, 7};/* only odd (0) */
-    // uint8_t convert[8] = {8, 8, 0, 2, 8, 8, 1, 3};/* only even */
-    // uint8_t convert[8] = {4, 6, 8, 8, 5, 7, 8, 8};/* only odd (0) */
-    // uint8_t convert[8] = {8, 4, 6, 8, 8, 5, 7, 8};/* none */
     // epoch_log("%04X:%04X epoch_vww: %x, val %x DS %x SI %x ES %x DI %x %x\n", cs >> 4, cpu_state.pc, addr, val,DS,SI,ES,DI, epoch->crtc[LC_INTERLACE_AND_SKEW]);
     // epoch_log("%04X:%04X epoch_vww: %x, val %x cm %x\n", cs >> 4, cpu_state.pc, addr, val, epoch->crtmode);
     cycles -= video_timing_write_w;
     addr -= 0xA0000;
-    // addr &= 0xfffffffe;
-    // if (0) {
     if (!(epoch->crtmode & 0x02) && !(epoch->font24)) {
         uint32_t toaddr, bitnum;
-        // if (addr < 0xd0000) {
-        //     int index = (addr - 0xA0000) >> 7; /* 128 bytes per char */
-        //     addr &= 0x007f;
-        //     addr += 0xA0000 + 84 * index;
-        // epoch_log("%x %x\n", addr, index);
-        // } else if (addr >= 0xD8000) {
-        //     int index = (addr - 0xD8000) >> 7; /* 128 bytes per char */
-        //     addr &= 0x007f;
-        //     if (addr & 2) return;
-        //     addr >>= 1;
-        //     addr += 0xC0000 + 42 * index;
-        // epoch_log("%x %x\n", addr, index);
-        // } else
-        //     return;
-
-        // if (addr < 0xd0000) {
-        //     addr -= 0xA0000;
-        //     if (addr & 2)
-        //         return;
-        //     addr >>= 1;
-        //     addr += 0xA0000;
-        // } else if (addr >= 0xD8000) {
-        //     addr -= 0xD8000;
-        //     if (addr & 2)
-        //         return;
-        //     addr >>= 1;
-        //     addr += 0xD8000;
-        // } else
-        //     return;
-
-        // addr >>= 1;
-        // if(addr & 0x02)
-        //     addr--;
-        // addr ^= 0x06;
-        //addr &= 0xffffd;/* 1101 */
-        // addr >>= 1;
-        
-        // if (convert[(addr + 0) & 7] > 7)
-        //     return;  
-        // epoch_vram_write((addr & 0xffff8) + convert[(addr + 0) & 7], val & 0xff, epoch);
-        // epoch_vram_write((addr & 0xffff8) + convert[(addr + 1) & 7], val >> 8, epoch);
 
         /* rw one word with 9 bits */
         /* virtual: 20000h (0010b, 0011b) -> real: 00001h (0000b, 0001b) */
-        
         toaddr = getaddr_9bitword(addr);
         bitnum   = toaddr & 7;
         epoch_vram_write(toaddr, val & 0xff, epoch);
-        // epoch_log("%x %x\n", toaddr, val);
+        
         /* get 9th bit */
         toaddr >>= 3;
         toaddr += 0x20000; /* real: C0000h */
         val >>= 15;
-        // epoch_log("%x %x ", toaddr, val);
         val <<= bitnum;
-        // epoch_log("%x ", val);
-        val |= (epoch_vram_read(toaddr, epoch) & (~(1 << bitnum)));/* mask to update one bit */
+
+        /* mask to update one bit */
+        val |= (epoch_vram_read(toaddr, epoch) & (~(1 << bitnum)));
         epoch_vram_write(toaddr, val, epoch);
         // epoch_log("%x %x\n", toaddr, val);
         // epoch_log("%x %x\n", addr, val);
@@ -1343,72 +1269,17 @@ epoch_vram_writew(uint32_t addr, uint16_t val, void *priv)
     // epoch_log("%x %x\n", addr, val);
 }
 
-// static uint8_t
-// epoch_vram_readb(uint32_t addr, void *priv)
-// {
-//     epoch_t *epoch = (epoch_t *) priv;
-//     cycles -= video_timing_read_b;
-//     // return 0xff;
-//  //   epoch_log("%04X:%04X epoch_vrb: %x, val %x\n", cs >> 4, cpu_state.pc, addr, epoch_vram_read(addr, epoch));
-//     // return epoch_vram_read(addr, epoch);
-// }
-
 static uint16_t
 epoch_vram_readw(uint32_t addr, void *priv)
 {
     epoch_t *epoch = (epoch_t *) priv;
-    // uint8_t convert[8] = {0, 2, 4, 6, 1, 3, 5, 7};/* all but pos+-1 */
-    // uint8_t convert[8] = {0, 4, 8, 8, 8, 8, 8, 8};/* all but pos+-1 */
     cycles -= video_timing_read_w;
     addr -= 0xA0000;
     // epoch_log("%04X:%04X epoch_vrw: %x cm %x\n", cs >> 4, cpu_state.pc, addr, epoch->crtmode);
-    // addr &= 0xfffffffe;
-    //read 0->0,1 2->2,3 4->4,5 6->6,7
-    //read 0->0,2 2->1,3 4->4,6 6->5,7
-    // if (0) {
     if (!(epoch->crtmode & 0x02) && !(epoch->font24)) {
         uint16_t ret;
         uint32_t bitnum;
         uint32_t toaddr;
-        // if (addr < 0xd0000) {
-        //     int index = (addr - 0xA0000) >> 7; /* 128 bytes per char */
-        //     addr &= 0x007f;
-        //     addr += 0xA0000 + 84 * index;
-        // epoch_log("%x %x %x\n", addr, index, epoch_vram_read(addr, epoch) | (epoch_vram_read(addr + 1, epoch) << 8));
-        // } else if (addr >= 0xD8000) {
-        //     int index = (addr - 0xD8000) >> 7; /* 128 bytes per char */
-        //     addr &= 0x007f;
-        //     if (addr & 2) return EPOCH_INVALIDACCESS16;
-        //     addr >>= 1;
-        //     addr += 0xC0000 + 42 * index;
-        // epoch_log("%x %x %x\n", addr, index, epoch_vram_read(addr, epoch) | (epoch_vram_read(addr + 1, epoch) << 8));
-        // } else
-        //     return EPOCH_INVALIDACCESS16;
-
-        // if (addr < 0xd0000) {
-        //     addr -= 0xA0000;
-        //     if (addr & 2)
-        //         return EPOCH_INVALIDACCESS16;
-        //     addr >>= 1;
-        //     addr += 0xA0000;
-        // } else if (addr >= 0xD8000) {
-        //     addr -= 0xD8000;
-        //     if (addr & 2)
-        //         return EPOCH_INVALIDACCESS16;
-        //     addr >>= 1;
-        //     addr += 0xD8000;
-        // } else
-        //         return EPOCH_INVALIDACCESS16;
-
-        // if(addr & 0x02)
-        //     addr--;
-        // // addr ^= 0x06;
-        // addr >>= 1;
-
-        // if (convert[(addr + 0) & 7] > 7)
-        //     return 0;  
-        // return epoch_vram_read((addr & 0xffff8) + convert[addr & 7], epoch) | (epoch_vram_read((addr & 0xffff8) + convert[(addr + 1) & 7], epoch) << 8);
-        
         /* rw one word with 9 bits */
         /* virtual: 20000h (0010b, 0011b) -> real: 00001h (0000b, 0001b) */
         toaddr = getaddr_9bitword(addr);
@@ -1430,10 +1301,9 @@ static void
 epoch_cram_write(uint32_t addr, uint8_t val, void *priv)
 {
     epoch_t *epoch = (epoch_t *) priv;
-    // if ((addr & ~0xfff) != 0xE0000) return;
     addr &= EPOCH_MASK_CRAM;
     epoch->cram[addr] = val;
-    epoch->fullchange = changeframecount;
+    epoch->fullchange = 3;
     // epoch_log("cw %04X:%04X %04X %02X\n", cs >> 4, cpu_state.pc, addr, val);
 }
 static void
@@ -1458,8 +1328,6 @@ static uint8_t
 epoch_cram_read(uint32_t addr, void *priv)
 {
     epoch_t *epoch = (epoch_t *) priv;
-    // if ((addr & ~epoch_MASK_CRAM) != 0xE0000)
-    //     return epoch_INVALIDACCESS8;
     addr &= EPOCH_MASK_CRAM;
     return epoch->cram[addr];
 }
@@ -1495,7 +1363,6 @@ epoch_parity_readb(uint32_t addr, void *priv)
             return EPOCH_INVALIDACCESS8;
         }
     }
-    // return EPOCH_INVALIDACCESS8;
     return mem_read_ram(addr, priv);
 }
 
@@ -1533,8 +1400,6 @@ epoch_parity_writeb(uint32_t addr, uint8_t val, void *priv)
             return;
         }
     }
-    // if (val == 0xcb)
-    //     epoch_log("CB %04X:%04X %04X:%04X>%04X:%04X\n", cs >> 4, cpu_state.pc, DS, SI, ES, DI);
     mem_write_ram(addr, val, priv);
 }
 static void
@@ -2338,7 +2203,7 @@ epoch_init(UNUSED(const device_t *info))
     epoch->dispontime        = 1000ull << 32;
     epoch->dispofftime       = 1000ull << 32;
     // epoch->changedvram       = calloc(1,  (EPOCH_MASK_VRAMPLANE + 1) >> 9); /* XX000h */
-    changeframecount = 3;
+
     if (epoch->font24)
         epoch->pixelclock = EPOCH_PIXELCLOCK24;
     else