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Compaq portable support - #74

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AtomicLunchbox wants to merge 2 commits into
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AtomicLunchbox:compaq_portable_support
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Compaq portable support#74
AtomicLunchbox wants to merge 2 commits into
640-KB:mainfrom
AtomicLunchbox:compaq_portable_support

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@AtomicLunchbox

@AtomicLunchbox AtomicLunchbox commented Jul 26, 2026

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Added support for the video mode switching hotkeys to match the stock Compaq BIOS:

  • ctrl-alt-, for MDA mode
  • ctrl-alt-. for CGA mode

TODO

  • cursor handling isn't correct yet; tends to get set in the middle of the line vertically
  • test with an external CGA monitor
  • test with a Compaq EGA card (update: the card works, but mode switching does not)

I have this running on a real Compaq Portable. I would still consider this to be preliminary support, but it's good enough for me to leave in the machine.

compaq_glabios

@AtomicLunchbox
AtomicLunchbox force-pushed the compaq_portable_support branch from c5a9a47 to d5f3424 Compare August 15, 2026 16:35
@AtomicLunchbox

AtomicLunchbox commented Aug 15, 2026

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Updated this again to address some of the floppy weirdness. The Compaq Portable reads SW1 like the 5150 does, but the BIOS versions (at least C and above) ignore most of them. I've updated this pull request to treat them more like the 5150 block does, which is closer to what the Compaq documentation says they are for. I can boot from floppy with no errors now.

Additional note for anyone who might want to test this under emulation, there's a bug/deficiency in 86box that doesn't set the SW1 switches correctly for the Compaq VDU and it will cause GLaBIOS to fail because it assumes there's a missing EGA or VGA card. You can still boot the the BIOS if you use a different video card.

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