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prime
May 28th, 2012, 12:53 AM
Hi,

In my vintage PCs I tend to try and fit a VGA card as I have more VGA monitors than anything else, however I have an issue they don't detect my monitors as colour and come up in mono VGA mode which is annoying.

For example the Cirrus logic 16 bit card in my AT only detects the colour monitor about 50% of the time, the rest it starts in mono.

Is there any way I can fool the card into always believing the monitor is colour ? as I only have colour monitors.

Cheers.

Phill.

nestor
May 28th, 2012, 01:35 AM
The key is in the VGA pins 11, 12 and 15. In old VGA only monitors, these pins were used to identify color and monochrome monitors. In newer SVGA monitors, these pins are used to provide EDID (a modern protocol to do the same thing, including resolutions). The problem here is you are using old VGA cards and new SVGA monitors.

I don't have Cirrus Logic VGAs, but Trident VGAs have a small utility called smonitor to manually configure the monitor type.

marcoguy
May 28th, 2012, 04:18 AM
That is kind of weird. I have a really old VGA card, and I use it sometimes with an HD widescreen monitor with fine color.

pearce_jj
May 28th, 2012, 04:51 AM
perhaps that card makes no attempt to check.

marcoguy
May 28th, 2012, 05:00 AM
Probably. I guess I am just lucky!

prime
May 28th, 2012, 05:39 AM
The key is in the VGA pins 11, 12 and 15. In old VGA only monitors, these pins were used to identify color and monochrome monitors. In newer SVGA monitors, these pins are used to provide EDID (a modern protocol to do the same thing, including resolutions). The problem here is you are using old VGA cards and new SVGA monitors.



Ahh, yeah that makes sense..... looks like this page documents the differences :

http://pinouts.ru/Video/VGA15_pinout.shtml

It should be possible to make an adapter that connects most of the signals through, but allows me to jumper, or dip switch pins 11,12 & 15 to ground as needed.

Though since I'm only ever going to be using a colour VGA on this card (I don't have any mono nor any non 1024x768 capable monitors any longer), I might just jumper pins 4 and 11 to ground with a 4.7K or something similar..... on the card.

Cheers.

Phill.

pearce_jj
May 28th, 2012, 05:43 AM
There must be pull-up resistors on the card (to detect the n/c) so they just need to be tied straight to ground in the cable I would have thought. Otherwise a voltage divider is created and the results will be unpredictable.