From 38e044ca34b40d77c66f1c525ce0c6fb0938756f Mon Sep 17 00:00:00 2001
From: TC1995 <mariogplayer90@gmail.com>
Date: Tue, 2 Apr 2024 15:09:18 +0200
Subject: [PATCH] Tseng Labs fixes and bug-compatible fixes too.

ET3000AX: the chip in question should not support 1MB of video memory.
ET4000AX: the early TC6058AF revision can support 1MB of video memory (e.g.: Diamond Speedstar BIOS D3.10, undumped anyway), and actually don't update the rowoffset to 256 when using such chip in 320x200x256 mode. Fixes the copper demo in said chip revision.
---
 src/include/86box/vid_svga.h |  1 +
 src/video/vid_et3000.c       |  2 --
 src/video/vid_et4000.c       | 19 +++++++++----------
 3 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/src/include/86box/vid_svga.h b/src/include/86box/vid_svga.h
index 2f8a83a1d..bc33ac746 100644
--- a/src/include/86box/vid_svga.h
+++ b/src/include/86box/vid_svga.h
@@ -129,6 +129,7 @@ typedef struct svga_t {
     int hblank_end_mask;
     int hblank_sub;
     int packed_4bpp;
+    int ps_bit_bug;
     int ati_4color;
 
     /*The three variables below allow us to implement memory maps like that seen on a 1MB Trio64 :
diff --git a/src/video/vid_et3000.c b/src/video/vid_et3000.c
index 97da08822..a7d2a749f 100644
--- a/src/video/vid_et3000.c
+++ b/src/video/vid_et3000.c
@@ -557,8 +557,6 @@ static const device_config_t et3000_config[] = {
               .value       = 256 },
           { .description = "512 KB",
               .value       = 512 },
-          { .description = "1 MB",
-              .value       = 1024 },
           { .description = "" } } },
     { .type = CONFIG_END }
 };
diff --git a/src/video/vid_et4000.c b/src/video/vid_et4000.c
index 7ceacb823..583487c5f 100644
--- a/src/video/vid_et4000.c
+++ b/src/video/vid_et4000.c
@@ -652,7 +652,9 @@ et4000_recalctimings(svga_t *svga)
 
     svga->ma_latch |= (svga->crtc[0x33] & 3) << 16;
 
-    svga->hblankstart    = (((svga->crtc[0x3f] & 0x4) >> 2) << 8) + svga->crtc[2];
+    svga->hblankstart = (((svga->crtc[0x3f] & 0x4) >> 2) << 8) + svga->crtc[2];
+
+    svga->ps_bit_bug = (dev->type == ET4000_TYPE_TC6058AF) && svga->lowres && ((svga->gdcreg[5] & 0x60) >= 0x40);
 
     if (svga->crtc[0x35] & 1)
         svga->vblankstart |= 0x400;
@@ -664,7 +666,7 @@ et4000_recalctimings(svga_t *svga)
         svga->vsyncstart |= 0x400;
     if (svga->crtc[0x35] & 0x10)
         svga->split |= 0x400;
-    if (!svga->rowoffset)
+    if (!svga->rowoffset && !svga->ps_bit_bug)
         svga->rowoffset = 0x100;
     if (svga->crtc[0x3f] & 1)
         svga->htotal |= 0x100;
@@ -729,13 +731,6 @@ et4000_recalctimings(svga_t *svga)
         svga->rowoffset <<= 1;
         svga->render = svga_render_8bpp_highres;
     }
-
-    if (dev->type == ET4000_TYPE_TC6058AF) {
-        if (svga->render == svga_render_8bpp_lowres)
-            svga->render = svga_render_8bpp_tseng_lowres;
-        else if (svga->render == svga_render_8bpp_highres)
-            svga->render = svga_render_8bpp_tseng_highres;
-    }
 }
 
 static void
@@ -962,6 +957,10 @@ static const device_config_t et4000_tc6058af_config[] = {
                 .description = "512 KB",
                 .value = 512
             },
+            {
+                .description = "1 MB",
+                .value = 1024
+            },
             {
                 .description = ""
             }
@@ -1071,7 +1070,7 @@ const device_t et4000_tc6058af_isa_device = {
     .name          = "Tseng Labs ET4000AX (TC6058AF) (ISA)",
     .internal_name = "et4000ax_tc6058af",
     .flags         = DEVICE_ISA,
-    .local         = 0,
+    .local         = ET4000_TYPE_TC6058AF,
     .init          = et4000_init,
     .close         = et4000_close,
     .reset         = NULL,