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int 21h
August 8th, 2012, 09:56 AM
Hi there,
Is there any easy way to tell if a video card is EGA or CGA considering they have the same connector?
I have an IBM XT which has an EGA card and monitor, and I just acquired another one but I have no idea if it is EGA or CGA and I don't want to risk damaging either the monitor or card...
The main chip on it is a MC6845P and there's a sticker on it marked "1501985 340311 V0011"
Thanks

Chuck(G)
August 8th, 2012, 10:29 AM
Many EGA cards can be configured to drive a CGA monitor. Also note that a monochrome display adapter also has a 9 pin D-sub as its output connector.

If the only oscillator or crystal on the board is a 14.318 MHz unit, it's a CGA. If the only crystal or oscillator is a 16.257 MHz, it's MDA/MGA. If there are several crystals or oscillators, one having a higher frequency, it's likely an EGA.

However, also note that the Plantronics color and Hercules Incolor also have DE9 outputs.

A photo of the card would cinch the identification.

int 21h
August 8th, 2012, 10:37 AM
Thanks for that!
Yeah it is the 16.257MHz one. I wasn't aware of MDA; I assumed it was EGA (my other IBM) but hey, you learn something new everyday!
http://i218.photobucket.com/albums/cc167/cnc95fan/IMG_3762.jpg
http://i218.photobucket.com/albums/cc167/cnc95fan/IMG_3764.jpg
http://i218.photobucket.com/albums/cc167/cnc95fan/IMG_3765.jpg

JohnElliott
August 8th, 2012, 10:38 AM
Googling 'ibm 1501985' suggests it's an MDA.

Edit: Ha, ninja'd! Yes, that's an MDA.

vwestlife
August 8th, 2012, 10:54 AM
Googling 'ibm 1501985' suggests it's an MDA.

Also where it says "Black & White/Parallel" on the board. :)

But actually that's a misnomer -- MDA was "black & green"!

And generally only MDA/Hercules video cards will have a printer port. There were some switchable MDA/Hercules/CGA combo video cards made in the early '90s that also had a printer port, but those are rare.

reenigne
August 8th, 2012, 11:03 AM
I have one more thing to add to the thread - if your EGA monitor is a 5154 it can (according to http://newsgroups.derkeiler.com/Archive/Comp/comp.sys.ibm.pc.classic/2006-03/msg00069.html) sync to various different frequencies and display output from an EGA, CGA or MDA card. However, the colours it generates from an MDA signal will be weird - either dark blue, dark green or dark cyan depending on the attribute.

Great Hierophant
August 8th, 2012, 01:20 PM
I have one more thing to add to the thread - if your EGA monitor is a 5154 it can (according to http://newsgroups.derkeiler.com/Archive/Comp/comp.sys.ibm.pc.classic/2006-03/msg00069.html) sync to various different frequencies and display output from an EGA, CGA or MDA card. However, the colours it generates from an MDA signal will be weird - either dark blue, dark green or dark cyan depending on the attribute.

I wouldn't trust that source, I am the author of it and was quite ignorant in those days. I have never had a 5154, so that is speculation as fixed frequency monitors tend not to like frequencies out of range. There are other inaccuracies there as well. It is unknown whether it can actually accept the horizontal and vertical scan frequencies of MDA. Contrary to what I posted there six years ago, the 5154 can properly display all CGA colors from a CGA card when set to 200-line mode.

Chuck(G)
August 8th, 2012, 01:23 PM
Regardless, don't try to run a CGA monitor from the card--it won't work.

reenigne
August 8th, 2012, 02:03 PM
Regardless, don't try to run a CGA monitor from the card--it won't work.

Indeed. Unless you do very silly things (http://www.reenigne.org/blog/i-bought-an-xt/) to make it work.

liudr
August 12th, 2012, 04:08 PM
Indeed. Unless you do very silly things (http://www.reenigne.org/blog/i-bought-an-xt/) to make it work.

So the very silly things have to involve an arduino, although it is not doing much more than a fake keyboard :)

wdegroot
August 13th, 2012, 11:52 AM
the rear commector makes it look like an original IBM mGA card with is capable of text only and nery little or NO graphics
the Hercules card is a more or less direct replacement
one givaway on a cga card it a 4 or 5 pin connector on the board near the back it is for a light pen.
the EGA card will have more ram and a switch at the back some thru an opening some internal.
the ega card is very useful and can be used with ega cga and mono monitoirs. do not experimant with settings if you havbe a mono monitor you can damage the monitor.
BUT setting an ega card to "CGA MONITOR" and using a CGA monitot is ok
in fact it vastly improves the colors and the ugly colors displayed with a cga card and monitor ( most games)
gives you real reds and blues.
This is practical based on experience not theory.
I ran an old XT with an ega card and a decent CGA monitor
to keep the kids off my system.