notes

src/hardware/vga_s3.cpp

@@ -715,6 +715,9 @@ void SVGA_Setup_S3Trio(void) {
 
     // Set CRTC 36 to specify amount of VRAM and PCI.
     // NTS: Apparently this register can't count beyond 4MB.
+    // The Windows 98 driver appears to read bits [7:5] as 4MB - (x * 512KB),
+    // for example x = 2 for 3MB, x = 7 for 512KB. Unusual sizes can be indicated
+    // such as x = 3 for 2.5MB which is what older versions of this code did.
     if (vga.mem.memsize < 1024*1024) {
         vga.mem.memsize = 512*1024;
         vga.s3.reg_36 = 0xfa;       // less than 1mb fast page mode