how to kludge a 486 PC into thinking it has a video card?

From: Jules Richardson <>
Date: Mon Feb 21 10:05:19 2005

On Sun, 2005-02-20 at 14:17 -0800, Steven Canning wrote:
> > On Fri, 18 Feb 2005, Jules Richardson wrote:
> >
> > > Far as I know the BIOSes of the time would check for MDA / CGA / EGA /
> > > VGA adapters at boot time, but 'not fitted' wasn't usually an option. I
> > > wonder if there's a clever way involving a minimum of circuitry in such
> > > a case for the BIOS checks to work...
> Why not just through a $2 Hercules Graphics card in an ISA slot and be done
> with it ? For troubleshooting you can spew graphics or text if needed....

Ahh, just trying to cut down on power consumption and keeping things
looking clean if possible. I can use serial console for all the boards
so for troubleshooting I'm OK once the BIOS has passed control the the
network boot ROM; about the only things that could go wrong before that
point anyway is catastrophic hardware failure or memory problems (the
latter assuming I'm using parity memory and the relevant BIOS even
checks anyway)

I wondered if there was some standard for the BIOS detecting card types
(write to this port, expect this value back kind of thing) that meant I
might be able to bodge something with a few LS logic chips, but maybe
not. Hopefully I can find enough boards with a BIOS that's sensible
enough not to check for video :)


Received on Mon Feb 21 2005 - 10:05:19 GMT

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