From 7a965efd907455e8a00924f176b678a8de656e1c Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Fri, 23 Aug 2024 06:21:27 +0200
Subject: [PATCH 1/3] Tandy and CGA: Implement the VSync interrupt, fixes
 Ghostbusters freezing.

---
 src/machine/m_tandy.c | 2 ++
 src/video/vid_cga.c   | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/src/machine/m_tandy.c b/src/machine/m_tandy.c
index d51209123..56982b3bd 100644
--- a/src/machine/m_tandy.c
+++ b/src/machine/m_tandy.c
@@ -27,6 +27,7 @@
 #include <86box/86box.h>
 #include <86box/timer.h>
 #include <86box/io.h>
+#include <86box/pic.h>
 #include <86box/pit.h>
 #include <86box/nmi.h>
 #include <86box/mem.h>
@@ -1215,6 +1216,7 @@ vid_poll(void *priv)
                 vid->dispon    = 0;
                 vid->displine  = 0;
                 vid->vsynctime = 16;
+                picint(1 << 5);
                 if (vid->crtc[7]) {
                     if (vid->mode & 1)
                         x = (vid->crtc[1] << 3) + 16;
diff --git a/src/video/vid_cga.c b/src/video/vid_cga.c
index 2ea07c346..8306edd56 100644
--- a/src/video/vid_cga.c
+++ b/src/video/vid_cga.c
@@ -28,6 +28,7 @@
 #include "cpu.h"
 #include <86box/io.h>
 #include <86box/timer.h>
+#include <86box/pic.h>
 #include <86box/pit.h>
 #include <86box/mem.h>
 #include <86box/rom.h>
@@ -607,6 +608,7 @@ cga_poll(void *priv)
                 cga->cgadispon = 0;
                 cga->displine  = 0;
                 cga->vsynctime = 16;
+                picint(1 << 5);
                 if (cga->crtc[7]) {
                     if (cga->cgamode & 1)
                         x = (cga->crtc[1] << 3) + 16;

From 1a961db422bd386535e45ccf172e1cd3d1febb1d Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Fri, 23 Aug 2024 07:09:35 +0200
Subject: [PATCH 2/3] CGA: Revert the VSync interrupt since the real CGA did
 not have that.

---
 src/video/vid_cga.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/src/video/vid_cga.c b/src/video/vid_cga.c
index 8306edd56..2ea07c346 100644
--- a/src/video/vid_cga.c
+++ b/src/video/vid_cga.c
@@ -28,7 +28,6 @@
 #include "cpu.h"
 #include <86box/io.h>
 #include <86box/timer.h>
-#include <86box/pic.h>
 #include <86box/pit.h>
 #include <86box/mem.h>
 #include <86box/rom.h>
@@ -608,7 +607,6 @@ cga_poll(void *priv)
                 cga->cgadispon = 0;
                 cga->displine  = 0;
                 cga->vsynctime = 16;
-                picint(1 << 5);
                 if (cga->crtc[7]) {
                     if (cga->cgamode & 1)
                         x = (cga->crtc[1] << 3) + 16;

From 0d43babac83a9a4e185e17a4880bb33d1d349aec Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Fri, 23 Aug 2024 07:14:43 +0200
Subject: [PATCH 3/3] Tandy: Slow down horizontal sync in low resolution modes.

---
 src/machine/m_tandy.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/machine/m_tandy.c b/src/machine/m_tandy.c
index 56982b3bd..2a7ef2275 100644
--- a/src/machine/m_tandy.c
+++ b/src/machine/m_tandy.c
@@ -718,8 +718,13 @@ recalc_timings(tandy_t *dev)
     double _dispofftime;
     double disptime;
 
-    disptime    = vid->crtc[0] + 1;
-    _dispontime = vid->crtc[1];
+    if (vid->mode & 1) {
+        disptime    = vid->crtc[0] + 1;
+        _dispontime = vid->crtc[1];
+    } else {
+        disptime    = (vid->crtc[0] + 1) << 1;
+        _dispontime = vid->crtc[1] << 1;
+    }
 
     _dispofftime = disptime - _dispontime;
     _dispontime *= CGACONST;
@@ -795,7 +800,10 @@ vid_out(uint16_t addr, uint8_t val, void *priv)
             break;
 
         case 0x03d8:
+            old = vid->mode;
             vid->mode = val;
+            if ((old ^ val) & 0x01)
+                recalc_timings(dev);
             if (!dev->is_sl2)
                 update_cga16_color(vid->mode);
             break;