From d00dafcf16cc8416901f9a9a1612750afb5ba0d1 Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Wed, 10 Jan 2024 23:30:48 +0100
Subject: [PATCH] Apply it to ATi 28800 and Mach 8 as well.

---
 src/video/vid_ati28800.c  | 7 +++++++
 src/video/vid_ati_mach8.c | 3 +++
 2 files changed, 10 insertions(+)

diff --git a/src/video/vid_ati28800.c b/src/video/vid_ati28800.c
index 09d6279f4..aed95b243 100644
--- a/src/video/vid_ati28800.c
+++ b/src/video/vid_ati28800.c
@@ -136,6 +136,10 @@ ati28800_out(uint16_t addr, uint8_t val, void *priv)
                     if ((old ^ val) & 0x80)
                         svga_recalctimings(svga);
                     break;
+                case 0xad:
+                    if ((old ^ val) & 0x0c)
+                        svga_recalctimings(svga);
+                    break;
                 case 0xb0:
                     if ((old ^ val) & 0x60)
                         svga_recalctimings(svga);
@@ -492,6 +496,9 @@ ati28800_recalctimings(svga_t *svga)
             }
         }
     }
+
+    if (ati28800->regs[0xad] & 0x08)
+        svga->hblankstart    = ((ati28800->regs[0x0d] >> 2) << 8) + svga->crtc[4] + 1;
 }
 
 static void
diff --git a/src/video/vid_ati_mach8.c b/src/video/vid_ati_mach8.c
index 21f6abd29..92ee59e19 100644
--- a/src/video/vid_ati_mach8.c
+++ b/src/video/vid_ati_mach8.c
@@ -2841,6 +2841,9 @@ mach_recalctimings(svga_t *svga)
             }
         }
     }
+
+    if (ati28800->regs[0xad] & 0x08)
+        svga->hblankstart    = ((ati28800->regs[0x0d] >> 2) << 8) + svga->crtc[4] + 1;
 }
 
 static void