IIRC, IBM standard supports dual video cards with the second adapter being monochrome.

I believe you need a dedicated monochrome adapter and monochrome CRT.

While I don't have a dedicated MDA card, I have tried a CGA card that has a MDA mode as well as a Hercules card with an EGA monitor. Unfortunately it didn't work, the EGA monitor couldn't display the modes correctly.

Pinout is different for VGA, so that would require some type of convertor/adapter. Not sure what exists for that.

Monochrome means monochrome, MDA or Hercules Mono, takes a different HMA than CGA, EGA, VGA, that's the only reason it works.

If you get lucky, you can find a TV or security monitor that synchs it with adjustment of vertical hold when you convert the 5V TTL signal down to 0.7V and put it in the composite video hole. Other ways to get lucky might include cheapy TV to VGA convertors which might turn it into something a multisynch monitor can synch, again converted first to 0.7V

Long ago I hooked up a mono monitor on a 386 that also had a VGA card. The mono adapter worked fine with the amber monitor and also the VGA worked.
Yes Only way to hook a VGA monitor to a mono adapter is with an active adapter.

I noticed that a lot of IBM MDA cards have a parallel port on them as well. What kind of problems might I anticipate if I were to try using one of these adapters, if the motherboard already had a parallel port?

EGA wonder seems to be capable of doing a composite mono mode...
https://www.minuszerodegrees.net/manuals/ATI/ … %20settings.htm

That should go straight into a TV or video monitor... or a VCR that has composite in so you can use it as a large RF modulator and get it on Analog Channel 3 or 4.

Kahenraz wrote on 2024-03-03, 04:09:

I noticed that a lot of IBM MDA cards have a parallel port on them as well. What kind of problems might I anticipate if I were to try using one of these adapters, if the motherboard already had a parallel port?

Easiest would be to just disable the onboard... otherwise IRQ reassignments might mess with your soundcard(s)

I suspect that whatever I have onboard will be a lot faster. There were several subsequent parallel port enhancements made over the years. I hope that it can be disabled on the card instead, but it's not clear whether this is possible.

Probably depends on the individual card. I have a Hercules card that a parallel port, but has no onboard way to disable it that I know of.

Used to find those 8bit mono/cga+parallel cards all over ebay for cheap, not any more. Think BitWrangler's idea is probably easiest if you can find or have a mono/cga/ega card with rca outputs.

I second that. You can use an original IBM MDA card or a Hercules or Hercules clone.

By default, any Hercules compatible card should behave like a basic IBM MDA.

The graphics menory is being disabled unless a game or driver (msherc, hgc etc) enables it.

So no worries, as a plain MDA card it can co-exist with CGA and EGA/VGA just fine.

If you like, you can use a signal converter from TTL video to VGA video. There might be some projects out there by now.

If not, the Graphics Gremlin might be an alternative.
It's a modern CGA/Hercules card with VGA connector.
I haven't tested it personally yet, though.
https://github.com/schlae/graphics-gremlin

Edit: It might also be possible to use an oscilloscope as a TTL monitor.
It can do those ~18KHz just fine, I think.
The principle should be same as using a scope as a TV monitor.
If the scope has X, Y and Z inputs it should do.

Edit: If everything fails, you can also hack an Hercules clone into being more VGA compatible.
However, the procedure isn't for beginners and there are several things to be taken into account.

Matching the voltage levels mostly, TTL uses +5v and that's a tad bit too high for any VGA input.
Second is timing. Multisync CRT monitors of the old days often had supported weird frequencies.
Modern flat screens usually don't.

Hercules graphics on VGA monitors (mod)

I think parallel ports on MDA cards are at 0x3BC ? Whereas other parallel ports are usually at 0x278 or 0x378. Probably wouldn't be an issue.

EGA/VGA cards can be configured through software to respond to the address ranges for either color or mono. Some cards also had dipswitches to choose the type of monitor. I wonder if you had the right cards, if you could just run two VGA monitors with one handling the monochrome modes.

I think the dual VGA thing needs a Goldilocks setup, not too early not too late. Not too early or the PCI graphics (you are not doing this with ISA methinks) won't respect the PnP sorting out, and you'll just get the triple beep adapter problem no POST. Too late and all the oldy timey modes have gone away. I have personally had dual PCI cards working on a 430TX board, so that's one pushpin in where the range is, I think 430FX maybe won't do it. Then I think it's needing the oldest, but still PnP Trident card you can find, I would say cirrus logic also, but never managed to get any but later ones working in dual mode. It stops win98 getting confused if they use different drivers so different cards helpful. Anyway, presuming you can get it to boot, and presuming you can find a util that works on the PCI cards, it has a snowball in an oven glove's chance in hell of working.

I think the easiest would be to install a dedicated monochrome display adapter with a separate monochrome monitor.
Since MDA occupies a different memory address space than either CGA, EGA or VGA, they can co-exist quite happily together.

Just make sure you don't "allocate " the MDA memory address space for other software to use (like using the I=B000-B7FF parameter in EMM386.EXE).

Just to clarify, I am talking about having a second ISA card that supports the necessary switches/jumpers to run as a mono card, like this one: https://www.minuszerodegrees.net/manuals/vide … nfiguration.txt

It's not clear whether it can run as a mono card and still output a VGA signal at the same time. If not, then it would effectively be the same as running a real mono card.

Right. yes, that should definitely do it, set to mono mode, with a mono monitor, the bit that concerns me as to whether it actually works with a VGA monitor is the "with their respective monitors" line.

bakemono wrote on 2024-03-04, 12:58:

Just to clarify, I am talking about having a second ISA card that supports the necessary switches/jumpers to run as a mono card, like this one: https://www.minuszerodegrees.net/manuals/vide … nfiguration.txt

It's not clear whether it can run as a mono card and still output a VGA signal at the same time. If not, then it would effectively be the same as running a real mono card.

Those cards usually can run as "super MDA", in a mode mostly software compatible with the original MDA and Hercules adapters, so MDA/Hercules software will work with them. Depending on DIP switches, they can display the "virtual MDA/Hercules" output on an actual MDA-type monitor or on a VGA monitor. Sounds great?

Forget it. All EGA/VGA cards that can "emulate mono" in varying degrees do not just use the mono I/O port range (3B0..3BF), but also the extended EGA I/O port range (3C0..3CF). In mono emulation mode, the cards do not use the CGA color I/O port range (3D0..3DF). You can only have one EGA/VGA type card, but you may combine it either with a CGA or an MDA/Hercules card (both of them do not use the 3C0..3CF range). You can not have two EGA/VGA cards, one in "hercules-like" and another one in "CGA-like" mode.

I don't know any card that is not EGA/VGA-like (i.e. it does not occupy 3C0..3CF) and is capable of displaying "monochrome text" with VGA timings (i.e. on a "modern monitor").

If you can get one of the multimode cards to put mono out of the 15pin and stay out of the color adapter address range, it's probably at the 18khz Hsynch. Then you'd need the CRT VGA multisynchs that Amiga and Atari folks chase that synch down to 15khz... normal VGA bottoms out at 31ish khz. Anyhow that's why I mentioned the cheapie video to VGA convertors early on, if they are doing simple scandoubling they might pitch it at 36ish khz which a decent CRT might lock.

So basically, replace one hard to find card/monitor combo with another hard to find card/monitor combo. Where the first one is very known to work and the second is full of maybes and might require testing 3+ cards and 3+ monitors to get a pair that do it. I have some weird cards and monitors around and will try to test any as they come across the bench, nothing meshes with near future plans though, so don't hold your breath, or urine, or put off any haircuts.

edit: Professor Farnsworth: Good news everyone, your friendly neighborhood industrial panels supplier can sort you out with a TTL MDA Mono capable LCD for a mere mid four figure price. (Don't pull that face, it does CGA too!)

I picked up an Oak Technologies OTI-037C for cheap on eBay. It has a dual VGA/Mono output. I think that it might be possible to disable the VGA portion through the dip switches, but I'll need to get some kind of retro box to convert the mono signal to VGA or HDMI regardless.

If I can't disable the VGA side, at least I can feel confident that it will work with this own built-in VGA. This must have been what was originally envisioned when the feature was implemented.

mkarcher wrote on 2024-03-04, 14:41:

Forget it. All EGA/VGA cards that can "emulate mono" in varying degrees do not just use the mono I/O port range (3B0..3BF), but also the extended EGA I/O port range (3C0..3CF). In mono emulation mode, the cards do not use the CGA color I/O port range (3D0..3DF). You can only have one EGA/VGA type card, but you may combine it either with a CGA or an MDA/Hercules card (both of them do not use the 3C0..3CF range). You can not have two EGA/VGA cards, one in "hercules-like" and another one in "CGA-like" mode.

Hi mkarcher, do you think this could be resolved by jumpering one of the cards to the 'alternate' 2xx I/O range?

I'm tempted to run an experiment, since I have both a Cirrus Logic GD-5x0 based card and a CHIPS 82C43x based one (although I might need to find the missing 28MHz oscillator)