Option 4 asks for a width and a height and then goes looking for a mode
that matches, instead of picking from three hardcoded numbers.
AX=4F00 returns a controller info block whose VideoModePtr is a far
pointer to a 0xFFFF-terminated list of mode numbers; each is asked what it
actually is with AX=4F01, and the first that reports the requested size at
32bpp wins. That is the fix for the table, not an addition to it -- the
table was wrong the first time it was written (0x146 was "1600x1200" and
is 320x200x8 here), and a table can only ever describe machines somebody
happened to test.
800x600 stays the floor: the console, the splash and Schcom all assume at
least that, and smaller would be a different set of assumptions rather
than a smaller number. Below it, or a size the BIOS cannot do, says so and
keeps 800x600 rather than failing to boot.
Scratch buffers at 0x31000 and 0x31200, clear of the mode info block at
0x30000 and everything else in that page -- the flags at +0x100, the e820
map at +0x208 and the RSDP slot at +0x600.
Verified over serial: 1280x800 comes up at 1280x800, which is in no table
anywhere and is the point; 640x480 is refused as below the minimum;
3000x2000 reports no such mode. Presets 1-3 and the no-key timeout are
unchanged. bootcheck 108 [ok]. stage2 is 20932 of 24576 bytes.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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