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

From: Randy McLaughlin <cctalk_at_randy482.com>
Date: Tue Feb 22 13:01:40 2005

From: "Eric J Korpela" <korpela_at_gmail.com>
Sent: Tuesday, February 22, 2005 12:33 PM
>> As long as you have a monitor that can handle the EGA frequency it should
>> be
>> no great effort to use a VGA monitor on an EGA card.
>
> A couple caveats here.....
>
> 1. Monitors that handle the frequency aren't being made much anymore.
> Most new
> monitors won't sync below 30kHz. Scan frequency conversion isn't
> impossible,
> but it certainly isn't easy.
>
> 2. EGA is a digital TTL level signal with 2 lines each for R G and B.
> When carrying
> CGA comaptible signals the low order green is the intensity bit.
> VGA is analog
> 0.7V p-p into 75 Ohm impedence. You need a 2-bit DAC with level
> conversion for
> each line (which is fancy talk for a few resistors.)
>
> 3. Beware of EGA-VGA DE-9 to HD15 adapters. They are usually 9-pin VGA
> to
> 15 pin VGA adapters, which is entirely different.
>
> Eric

As you and I pointed out as long as you have a monitor that can handle the
EGA frequency it should be no great effort to use a VGA monitor on an EGA
card.


Randy
Received on Tue Feb 22 2005 - 13:01:40 GMT