Looking for a VGA card that can drive an MDA monitor

Looking for a VGA card that can drive an MDA monitor - what are my options?

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First post, by KenjiUmino

Posted on 2025-05-12, 23:19

KenjiUmino Offline

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Now that I finally got around and converted my 120V-only IBM 5151 Monitor to run on 230V, I want to use it again on the IBM 5170 PC that It came with.

There was a Hercules card installed in the 5170 and I could just put that card back in and keep using it, but even though a Hercules is a LOT more versatile than a plain MDA card, compatibility with games is still pretty limited compared to CGA/EGA/VGA cards, and the various "CGA to Hercules" software tools seem to be pretty "hit and miss" ... from my own bit of testing I got the impression they seem to lean more towards "miss".

... and then I stumbled upon this thread here on vogons with plenty of back and forth discussion about which EGA card produces the best image on an MDA monitor.

While reading thru these posts I was like "Wait - EGA on MDA monitors? That was a thing?" - well, apparently it was, and I found out that there are even some VGA cards out there that have a 9 Pin monitor connector in addition to the 15 pin VGA and, If I understand correctly, these cards can output anything to any monitor, be it MDA, CGA, EGA, VGA.

And now I want one 😉

So what's out there ?

So far, I have found out that there is the ATI VGA Wonder in 8 and 16 bit versions ... but a short look on ebay told me that these are NOT the cards I am looking for ... those prices are just crazy ... do they really expect me to pay more for a decades old graphics card than what I payed for the barely used RX 7700XT that I bought myself for christmas ??? SRSLY ???

While slowly recovering from the shock but still looking at these ATI cards, ebay suggested some more VGA cards to me that seem to fit the bill:

Some of the cards are built around the Trident TVGA 8800CS chip, have both 9 pin and 15 pin monitor connectors ... and are a LOT cheaper than the ATI cards.

The other bunch of cards ebay suggested are Tseng ET 3000 based cards ... also with both types of monitor connector ... also a LOT cheaper than the ATI stuff.

Soooo ... does anyone have hands on experience running any of these with an MDA monitor ?
Should I go for a Trident based card or a Tseng based one?

I read that the Trident 8800SC is very slow ... but HOW slow ... and will it even make a difference on this 6 MHz 286 PC with barely any RAM ...

Did any other brands make TTL monitor compatible VGA chipsets like this? Cirrus logic? Genoa?

Reply 1 of 7, by DEAT

Posted on 2025-05-15, 06:20

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KenjiUmino wrote on 2025-05-12, 23:19:
Some of the cards are built around the Trident TVGA 8800CS chip, have both 9 pin and 15 pin monitor connectors ... and are a LOT […]
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Some of the cards are built around the Trident TVGA 8800CS chip, have both 9 pin and 15 pin monitor connectors ... and are a LOT cheaper than the ATI cards.

The other bunch of cards ebay suggested are Tseng ET 3000 based cards ... also with both types of monitor connector ... also a LOT cheaper than the ATI stuff.

Soooo ... does anyone have hands on experience running any of these with an MDA monitor ?
Should I go for a Trident based card or a Tseng based one?

Do you care about MDA only, or do you want Hercules graphics? Tseng ET3000 cards do not output Hercules via TTL, only through VGA emulation. I've had no success with outputting via TTL with my TVGA8800CS.

If you want Hercules output via TTL, Oak OTI067 cards are the best choice that you shouldn't have too much trouble finding.

Reply 2 of 7, by Jo22

Posted on 2025-05-15, 07:50

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Hi. I think that non-IBM EGA cards can do these three things, essentially.
- use an MDA monitor for Hercules emulation
- use an MDA monitor for EGA's mode 0Fh (640x350 black white)
- support MDA monitor for displaying EGA's mode 10h (640x350 pels 16c) using interlacing

The ATI EGA Wonder did support this, I believe. There's an advertisement.
Not sure about CGA and 200 line EGA, though.

What's not working via TTL is VGA mode support.
Well, technically there is - but only for mono and 16c modes on a multiy sync monitor.
Games that use 320x200 256c (mode 13h) won't work on an MDA monitor.

If you like that, an Amdek monitor with a composite input is a better choice.
It looks similar to an MDA monitor but can take an AV signal.
That way, an VGA-Composite converter, a custom cable+DOS TSR or an CGA card with composite out can be used.

But that's just my opinion, of course.

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Reply 3 of 7, by digger

Posted on 2025-05-15, 08:52

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I have such a set-up, with an ATI VGA Wonder-16 hooked up to an IBM 5151 monitor. It allows for all EGA modes on this monochrome monitor, including the color modes, shown in greyscale.

It even pulls off 16 shades of grey on that monitor, through the use of pulse-width modulation (PWM) techniques. This results in way better graphics on this monitor than it was ever designed by IBM to show. Pretty cool!

It does not support any VGA modes this way. EGA compatibility is the best it can do with MDA/Hercules monitors, and that's pretty impressive already.

One caveat that I still need to look into, though: 16-color 320x200 mode results in a constantly vertically scrolling (non-sync-locked) screen. Apparently, one of the internal potentiometers in this monitor (that aren't accessible without opening up the monitor) control Vertical Hold, and I'll probably need to fiddle with that one to get the 16-color 320x200 mode to be stable. Strangely enough, this is neither an issue in 4-color CGA 320x200 mode nor in 16-color 640x350 mode. I really hope I can tweak it in a way that all EGA modes are stable, without constantly having to tweak it differently for different graphics/resolution modes.

Any advice here would be welcome, by the way.

Reply 4 of 7, by KenjiUmino

Posted on 2025-05-16, 00:22

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Hey, thanks for the replies everyone ... let's see if I got this straight ...

digger wrote on 2025-05-15, 08:52:

I have such a set-up, with an ATI VGA Wonder-16 hooked up to an IBM 5151 monitor. It allows for all EGA modes on this monochrome monitor, including the color modes, shown in greyscale.

It even pulls off 16 shades of grey on that monitor, through the use of pulse-width modulation (PWM) techniques. This results in way better graphics on this monitor than it was ever designed by IBM to show. Pretty cool!

It does not support any VGA modes this way. EGA compatibility is the best it can do with MDA/Hercules monitors, and that's pretty impressive already.

Impressive indeed ... but still a bit of a bummer with regards to what I had in mind ... I wondered how they'd do 640x480 on a monitor that is designed to only do 350 lines and nothing else ... well now I know. 🤣

Can you tell me more about the behavior of this card ?

Does the ATI VGA wonder behave any different when configured for TTL monochrome ... like ... report itself as an EGA card to the system ... or report as a VGA card but simply refuse to switch to any VGA mode? Or does it report as a VGA card, switch to VGA modes and just use the 15 pin output exclusively in these modes?

Does the VGA wonder display anything on the 15 pin at all when it is configured for a TTL monitor?
I could see that being a useful gimmick for capturing gameplay from the 15 pin while actually playing on the TTL monitor connected to the 9 pin.

digger wrote on 2025-05-15, 08:52:

One caveat that I still need to look into, though: 16-color 320x200 mode results in a constantly vertically scrolling (non-sync-locked) screen. Apparently, one of the internal potentiometers in this monitor (that aren't accessible without opening up the monitor) control Vertical Hold, and I'll probably need to fiddle with that one to get the 16-color 320x200 mode to be stable. Strangely enough, this is neither an issue in 4-color CGA 320x200 mode nor in 16-color 640x350 mode. I really hope I can tweak it in a way that all EGA modes are stable, without constantly having to tweak it differently for different graphics/resolution modes.

Any advice here would be welcome, by the way.

Well, getting inside the 5151 is easy - just half a dozen eeeezy steps ...
If you have not been inside one yet, I can tell you how I did it so you can follow along ...

Just keep in mind that you do what I did at your own risk, disclaimer, yadda yadda ... just be careful in there, because ... y'know ... delicate glass tube 'n' high voltage 'n' shit ...

Here goes:

0. unplug the video and power cord from the computer (if not done so already)

1. Remove two square clip-in plastic cover thingies on the top of the monitor - be gentle, because that old plastic might have become brittle.
Under these plastic thingies, there should be two brass colored screws you need to get out - that's all for the top side.

2. With the top done, turn the monitor on its face so you can get to the screws on the underside, free the mains and video cable from the plastic holder thing on the back cover, then remove the black screws .
You don't need to touch the screws that hold the rubber feet on, or the two brass colored screws that hide under the white stickers - actually, leave those two screws alone - these keep the plate that holds the transformer from falling down onto the tube once you have removed the black screws.

3. Pull and wiggle the top cover off.
Now put the monitor back on its feet - as the transformer & its mounting plate is about the heaviest single part in this monitor besides the glass tube, and now only attached to the front plastic frame by those two screws, the whole assembly wobbles around quite a bit so you may want to support the plate with your third hand whenever you are flipping the monitor around.

4. There are a bunch of potentiometers along the top edge of the big circuit board (they had white plastic caps on mine but pictures on the internet show that they also come in black) ... they should all have a flathead compatible slot in the plastic and what they do should be written on the PCB ... the one you are looking for should be right towards the front of the monitor in the "vertical" section ...

5. now comes the fun part: plug the monitor back in and turn the computer on.
If you see an image, congratulations - nothing has been damaged yet.

6. With the computer displaying the desired video modes, grab a sufficiently large and long flat head screwdriver and adjust those potentiometers as needed ... just make sure to touch nothing else on the board ... especially not in the "vertical" section where the flyback is...

good luck

And if you absolutely can't get it to a point where all EGA modes are stable, you could remove that pot from the board and put some wires there so you can mount the pot in a more convenient spot where it is accessible without ripping the whole monitor apart every time you need to fiddle with it

Reply 5 of 7, by BitWrangler

Posted on 2025-05-16, 02:14

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This Oak OTI037 based "VG3000" has the 9 pin on it and works into a CGA monitor for sure, have not personally tested it on mono, but seems like it should do it. Re: Lowend 486 ISA VGA Graphics Quick Test, Mostly Tridents plus Oak, ATI, Tseng ....

Not sure if it does EGA on mono but should do CGA on mono I think.

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Reply 6 of 7, by dionb

Posted on 2025-05-22, 09:14

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BitWrangler wrote on 2025-05-16, 02:14:

This Oak OTI037 based "VG3000" has the 9 pin on it and works into a CGA monitor for sure, have not personally tested it on mono, but seems like it should do it. Re: Lowend 486 ISA VGA Graphics Quick Test, Mostly Tridents plus Oak, ATI, Tseng ....

Not sure if it does EGA on mono but should do CGA on mono I think.

The "VG3000" deserves more respect. It's a DFI card, one of the most compatible (if by no means fastest) early 16b ISA CGA cards: https://theretroweb.com/expansioncards/s/dfi-vg-3000

That said, this feature was pretty universal in the first generation of ISA VGA cards and you can find cards with Trident and Tseng chipsets doing it as well as the already mentioned Oak and ATi designs. ATi tended to have the best 'special sauce' for shoehorning output from other standards into mono modes, but if I ever find a more standard mono monitor (my only mono ones are an ancient Sony composite box and an Olivetti 25kHz beast) I might be tempted to do a comparison.

Reply 7 of 7, by VileR

Posted on 2025-05-22, 15:21

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digger wrote on 2025-05-15, 08:52:
One caveat that I still need to look into, though: 16-color 320x200 mode results in a constantly vertically scrolling (non-sync-locked) screen. Apparently, one of the internal potentiometers in this monitor (that aren't accessible without opening up the monitor) control Vertical Hold, and I'll probably need to fiddle with that one to get the 16-color 320x200 mode to be stable. Strangely enough, this is neither an issue in 4-color CGA 320x200 mode nor in 16-color 640x350 mode. I really hope I can tweak it in a way that all EGA modes are stable, without constantly having to tweak it differently for different graphics/resolution modes.

Any advice here would be welcome, by the way.

To figure it out, I guess the first step would be to look at the Video Parameter Table. Off the top of my head, I can't think of a reason why the 16-color and 4-color variants should have any difference in vertical timings. At least for normal VGA - maybe ATI's 5151 trickery needs the setup to be different somehow, but it sounds more likely that the VBIOS revision is buggy or something.

How is the card told to work with the 5151 - is it just a physical switch, or is there an additional piece of software that you run to tweak mode options? Are the 200-line modes double-scanned on the 5151?

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