The VDB is an analog splitter: the game's packed-16bpp trick routes the two
framebuffer bytes through the board palettes at 0x300/8/10, but any plain
VGA mode passes the S3's own DAC signal to every head -- no VDB register
traffic at all. The VGL_LABS test suite draws its secondary-display
patterns in 640x480x8 and programs nothing at 0x300-0x31A (verified from a
full session log), so the packed-only decode showed black heads. pal_draw
now branches: M_LIN8 decodes through the VGA DAC (full color on the color
heads, single-wire luminance on the mono MFD windows); 16bpp keeps the
packed VDB-palette decode.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
CydandClaude Fable 5
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