Yes of course, hercules is a superset of mda with graphics

Thank you!

Yep, should also work with cards that have a CGA monochrome mode, and some special cases of EGA monochrome like perhaps the ATI graphics wonder where you can specify a monitor type on jumperswitches. (Straight EGA mono would be wrong frequency)

BitWrangler wrote on 2022-12-14, 21:25:

Yep, should also work with cards that have a CGA monochrome mode, and some special cases of EGA monochrome like perhaps the ATI graphics wonder where you can specify a monitor type on jumperswitches. (Straight EGA mono would be wrong frequency)

Mostly wrong!

MDA/Hercules = 18 kHz HSYNC
CGA = 15 kHz HSYNC

So, in general, can't connect a CGA card to an MDA/Hercules monitor.
But there's plenty of monochrome monitors that support both 15 and 18 kHz.
Have a look at the monitor's plug - if all 9 pins are there, then it's likely to support both MDA/Hercules and CGA.
If some pins are missing, it must be MDA/Hercules only.

Also, the original IBM EGA and all proper clones can be DIP-switched to monochrome mode, ie. 18 kHz HSYNC.

Yeah unfortunately I did most of the playing around with that stuff in the fog of the early 90s before you could look stuff up online (Thought it took until 2000s for the older stuff to make it) and had 2 or 3 undocumented multimode cards so it was kinda guessing what they were doing with whatever rate.

Grzyb wrote on 2022-12-15, 01:43:

So, in general, can't connect a CGA card to an MDA/Hercules monitor.
But there's plenty of monochrome monitors that support both 15 and 18 kHz.

Another thing one must be careful of is mono monitors tolerating the 60Hz vertical refresh of CGA and appearing to work, with an audible high pitch sound. They will stop tolerating anything soon, guaranteed!

Thanks guys, I wasn't sure about this at all, it's my first MDA (Hitachi clone) adapter. I thought that the "original" IBM needed a special monitor to work with but luckily I was wrong. I didn't want to risk damaging the monitor with an incompatible card.

BitWrangler wrote on 2022-12-14, 21:25:

Yep, should also work with cards that have a CGA monochrome mode, and some special cases of EGA monochrome like perhaps the ATI graphics wonder where you can specify a monitor type on jumperswitches. (Straight EGA mono would be wrong frequency)

Just to make the things more clear on what is correct about this statement: There are cheap CGA/Hercules combo cards that can be jumpered / DIP switched to CGA or Hercules mode. If you switch this card to Hercules mode, it will work with an MDA monitor. On the other hand, there are a lot of 3rd-Party CGA cards that have a monochrome Cinch jack next to the color composite Chinch jack, or CGA card where you can switch the (single) Cinch jack between monochrome (VBS) and color composite (CVBS). Those cards always output CGA frequencies which are definitely unsuitable for the IBM 5151.

ATI had a lot of "magic" cards that ran "any mode on any monitor", and for sure they had solutions that could run Hercules applications on CGA monitors and vice-versa, as long as they were configured the right way.

Lastly, the IBM EGA card (and every proper clone) can (as Grzyb already explained) be set to "monochrome monitor", in which case it will run at MDA frequencies, at full 640x350 resolution (or 720x350 in text mode), but only support video modes 07h and 0Fh. It will coexist with a CGA card in that configuration. On the other hand, if the EGA card is set to "EGA monitor" it will run at frequencies unsuitable for MDA monitors. I don't know whether there are monochrome monitors compatible with "EGA monitor" frequencies, except for monochrome multisync monitors that happen to work over the whole range of 15 to 22 kHz.

Just to add to the confusion it turns out that this Casper monitor is actually a monochrome EGA that works with a wide range of frequencies, not just MDA and hercules. Hercules was really popular here so everything that has an amber screen is called hercules now.

Miphee wrote on 2022-12-15, 20:14:

Just to add to the confusion it turns out that this Casper monitor is actually a monochrome EGA that works with a wide range of frequencies, not just MDA and hercules. Hercules was really popular here so everything that has an amber screen is called hercules now.

I'm not really sure about that. Your monitor looks like a Casper GM-1266 monitor. There is currently one of these on ebay, and the model plate on the back side has the model designation "HMM-1200" printed as part of the FCC ID. This is the Hyundai part number of that monitor that is obviously rebranded by Casper. Another vendor that rebranded this monitor is Commodore - they called it 1402. The service manual for the Commodore 1402 is available at archive.org. The schematics of that monitor in the back of the service manual reference the model number HMM-1200. The specification in that manual describe the monitor as MDA-only (horizontal: 18.432 kHz, vertical: 50Hz). The schematics of the horizontal deflection circuit in that manual look very similar to the IBM 5151 horizontal deflection circuit. I highly recommend to not drive that monitor with CGA frequencies (15.6kHz), as this might damage this kind of circuit. If you were to connect that monitor to an EGA card in "EGA monitor mode", the monitor will be driven at 21.8kHz in text and high-res graphics mode (which it will likely survive, although with a quite tall picture), but driven at 15.6kHz in CGA-compatible and EGA low res graphics mode (which might break the monitor). Please do not connect that monitor to anything that might generate CGA frequencies.

As I already explained, a EGA card configured as monochrome card does not require an "EGA monitor", but is designed to work with a MDA-type monitors like the Casper GM-1266. So you are right that this monitor is the correct type of monitor to be connected to an EGA card configured for "monochrome monitor", but calling the monitor a "monochrome EGA monitor" is misleading, as most people understand the term "EGA monitor" as "monitor supporting 21.8 and 15.6 kHz" (like the IBM 5154, the ECD) which the GM-1266 is not.

mkarcher wrote on 2022-12-15, 21:44:

I'm not really sure about that. Your monitor looks like a Casper GM-1266 monitor.

It's actually a Casper DS-1468GS. The few sources I found claims it's an EGA monochrome that supports CGA, hercules and MDA modes.
Just tested it with an EGA and CGA card in different jumper configurations, it worked. Guess I just found my new multisync test monitor. 😀

Now that's an uncommon monitor! Proper mono EGA screenshots will be a special thing for anyone interested.

Amber, I love amber! Cute monitor. 😍

Miphee wrote on 2022-12-16, 08:14:

It's actually a Casper DS-1468GS. The few sources I found claims it's an EGA monochrome that supports CGA, hercules and MDA modes.
Just tested it with an EGA and CGA card in different jumper configurations, it worked. Guess I just found my new multisync test monitor. 😀

Fair enough. I was unable to quickly find proper sources for more extensive monitor documentation, too. Your test pictures do not show a screen with EGA timings, though. The two EGA screenshots you posted are 200-line modes (the scanlines are clearly visible), in CGA-compatible 40-column and 80-column mode, so they run at CGA-compatible 15.6kHz and don't illustrate the EGA compatibility of that monitor. For an original IBM EGA card, it looks like you used the DIP switch settings on,off,off,on (40-column) and on,off,off,off or off,on,on,on (both 80-column). You only get high-resolution EGA text output in the DIP switch configuration off,on,on,off. High-resolution EGA text output should be comparable in quality to the MDA text output, whereas your current "ega.jpg" screenshot has text quality comparable to the CGA output in "cga.jpg".

I also love those amber monitors, my all time favourite monochrome!

mkarcher wrote on 2022-12-16, 12:21:

High-resolution EGA text output should be comparable in quality to the MDA text output, whereas your current "ega.jpg" screenshot has text quality comparable to the CGA output in "cga.jpg".

Man, this shit is complicated! 😁
I tried with a standard noname clone CGA card that had no jumpers (cga.jpg) and a PA-WTEGA clone. I tried off-on-on-off and that is ega2.jpg with the oversized text.
Does that mean that it's not really EGA, it's just some compatibility mode on the cards auto-detecting that the monitor is MDA only? Or is it compatible with EGA but text only?

Miphee wrote on 2022-12-16, 17:06:

mkarcher wrote on 2022-12-16, 12:21:

High-resolution EGA text output should be comparable in quality to the MDA text output, whereas your current "ega.jpg" screenshot has text quality comparable to the CGA output in "cga.jpg".

I tried with a standard noname clone CGA card that had no jumpers (cga.jpg)

cga.jpg looks just as CGA text in 80x25 mode is supposed to look. No issues with that.

Miphee wrote on 2022-12-16, 17:06:

and a PA-WTEGA clone. I tried off-on-on-off and that is ega2.jpg with the oversized text.
Does that mean that it's not really EGA, it's just some compatibility mode on the cards auto-detecting that the monitor is MDA only? Or is it compatible with EGA but text only?

The correct technical term for the "oversized text" is "CGA-compatible 40-character mode". The DIP-switch setting for an IBM EGA card to boot up as primary video card in CGA-compatible 40-character mode is "on-off-off-on". I suppose your PT-WTEGA clone is not sufficiently labelled to indicate what position of the switch is "on" and what position is "off", or it uses inverted logic compared to the IBM EGA card. Try again with all four DIP switches in the opposite settings of what you had when your took the ega2.jpg image.

mkarcher wrote on 2022-12-16, 18:08:

The correct technical term for the "oversized text" is "CGA-compatible 40-character mode". The DIP-switch setting for an IBM EGA card to boot up as primary video card in CGA-compatible 40-character mode is "on-off-off-on". I suppose your PT-WTEGA clone is not sufficiently labelled to indicate what position of the switch is "on" and what position is "off", or it uses inverted logic compared to the IBM EGA card. Try again with all four DIP switches in the opposite settings of what you had when your took the ega2.jpg image.

I have to build a DOS rig with games on it to test this monitor to be sure but it seems that it's not EGA, just the EGA card playing tricks on me. I tried all possible combinations with the PT-WTEGA and all worked, but I have no games to confirm this so I'll build one soon. Thanks for the help.

Miphee wrote on 2022-12-16, 17:06:

I also love those amber monitors, my all time favourite monochrome! […]
Show full quote

I also love those amber monitors, my all time favourite monochrome!

mkarcher wrote on 2022-12-16, 12:21:

High-resolution EGA text output should be comparable in quality to the MDA text output, whereas your current "ega.jpg" screenshot has text quality comparable to the CGA output in "cga.jpg".

Man, this shit is complicated! 😁
...

It's actually less complicated than it sounds - the BIOS and POST screens in real EGA mode also look quite similar to the same screens in VGA mode, font-wise. The difference between this and the screenshots you've posted (40 and 80-col CGA compatible mode) should be quite visible - the fonts in real EGA look more "hi-res" with less visible scanlines.