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

From: Steve Thatcher <>
Date: Mon Feb 21 11:04:13 2005

assumptions with solutions are better than simply telling people to use a
video card when it was stated that was not the desire...

as for things being different between manufacturers, of course it is. As I
always told engineers when I was giving a technical presentation for
in-circuit emulators that I designed, "not everyone when to the same
school, therefore every design is different..."

A single CPLD from Xilinx can be put on a card and be the entire
"programmable" solution. The current consumption would be minor compared to
all the chips necessary for a real video card.

best regards, Steve Thatcher

At 11:35 AM 02/21/2005, you wrote:
>On Mon, Feb 21, 2005 at 11:26:33AM -0500, Steve Thatcher wrote:
> > in order for you to fool the bios you will need some hardware that will
> > "respond" to key areas that the bios is interested in.
> >
> > Picking a mono card as a target, you will need hardware that allows for
> > writes and reads of memory from b000:0 to b000:7fff (the end address
> may be
> > a lower location). I don't think the bios does a real memory test, so you
> > may be able to use one register that lets the cpu write a value to it that
> > can be read back (the register should respond to all addresses in the
> range.
>This is an assumption; I know for a fact that different BIOS
>manufacturers check in different ways; for example, Award vs.
>Phoenix vs. AMI. Some write to registers; some write to video RAM;
>some do both; some do neither (read $3d8 for verticle retrace
>status or other methods).
>The only universal/compatible way to fool the BIOS into thinking a
>card is in the machine is to *put a card in the machine*.
>Jim Leonard Email:
>Like PC games? Help support the MobyGames
>Or taste a slice of the demoscene at
Received on Mon Feb 21 2005 - 11:04:13 GMT

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