MDA works alongside any color adapter

jasa1063 wrote on 2022-09-10, 16:39:

I am currently building out my 2nd Epson Equity Ie computer. I have a rare STB Chauffeur HT I would like to install alongside the MCGA with the STB card configured for Hercules mode. The IBM PS/2 Model 30 did not have a monochrome text available only the 640x480x2 graphics mode. Since the Epson Equity Ie is clone of the IBM PS/2 Model 30, would the BIOS support it? Just wondering if anyone knows the answer.

Why do you want MCGA to operate in monochrome mode ?
It supports the following test modes in color (in addition to the CGA ones):

40 x 25 text (8 x 16 char. box) with 16 colors
80 x 25 text (8 x 16 char. box) with 16 colors

Additionally,.

1The integrated MCGA will automatically use up to 64 shades of gray in converting color modes of operations for display on the IBM 8525-001/-G01 (monochrome model) *. This allows users who prefer a monochrome display to execute color graphics applications.

* actually analogue greyscale, AFAIU

If what you want is to convince an MCGA to switch to greyscale mode (including for its text modes), there is a way to do that so by setting some registers ( http://bitsavers.org/pdf/ibm/pc/ps2/PS2_Model … rence_Jun87.pdf ), and likely also a way to do so by modifying a VGA cable (don't recall exactly how).

Also, the MCGA will output analogue RGB (like VGA) and will not work with a TTL monochrome monitor like those typically used with MDA or Hercules monochrome nor will it work with a CGA monitor (digital RGB), unless converters are used .

Additional info : https://www.ardent-tool.com/video/MCGA.html#Modes

EDIT : I may have misunderstood your question . Lack of system BIOS support should not stop your Hercules card from working, but I presume (could be wrong) that the system will consider its onboard MCGA as the "primary" adapter and will initialize only it at boot. You would then be free to use Hercules compatible graphics software on the computer using your other card and its attached monitor.

darry wrote on 2022-09-10, 17:46:

Why do you want MCGA to operate in monochrome mode ? It supports the following test modes in color (in addition to the CGA one […]
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jasa1063 wrote on 2022-09-10, 16:39:

I am currently building out my 2nd Epson Equity Ie computer. I have a rare STB Chauffeur HT I would like to install alongside the MCGA with the STB card configured for Hercules mode. The IBM PS/2 Model 30 did not have a monochrome text available only the 640x480x2 graphics mode. Since the Epson Equity Ie is clone of the IBM PS/2 Model 30, would the BIOS support it? Just wondering if anyone knows the answer.

Why do you want MCGA to operate in monochrome mode ?
It supports the following test modes in color (in addition to the CGA ones):

40 x 25 text (8 x 16 char. box) with 16 colors
80 x 25 text (8 x 16 char. box) with 16 colors

Additionally,.

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1The integrated MCGA will automatically use up to 64 shades of gray in converting color modes of operations for display on the IBM 8525-001/-G01 (monochrome model) *. This allows users who prefer a monochrome display to execute color graphics applications.

* actually analogue greyscale, AFAIU

If what you want is to convince an MCGA to switch to greyscale mode (including for its text modes), there is a way to do that so by setting some registers ( http://bitsavers.org/pdf/ibm/pc/ps2/PS2_Model … rence_Jun87.pdf ), and likely also a way to do so by modifying a VGA cable (don't recall exactly how).

Also, the MCGA will output analogue RGB (like VGA) and will not work with a TTL monochrome monitor like those typically used with MDA or Hercules monochrome nor will it work with a CGA monitor (digital RGB), unless converters are used .

Additional info : https://www.ardent-tool.com/video/MCGA.html#Modes

EDIT : I may have misunderstood your question . Lack of system BIOS support should not stop your Hercules card from working, but I presume (could be wrong) that the system will consider its onboard MCGA as the "primary" adapter and will initialize only it at boot. You would then be free to use Hercules compatible graphics software on the computer using your other card and its attached monitor.

Let me clarify a few things. I would be using a separate monitor for the Hercules output. The Epson Equity Ie and IBM PS/2 Model 25/30 do not have an 80x25 monochrome mode. If one where to switch to the Hercules adapter by using the MODE MONO command, would there be any character output or not? I am wondering if there is a lack of BIOS support on these computers for monochrome text output. I have the STB Chauffeur HT in storage and do not want to dig it out if this is not going to work

Got this link with my post on this subject on vcfed.org to this Epson suipport bulletiin and it says you can use a Hercules card with the Epson Equity Ie.

https://files.support.epson.com/pdf/e1e___/e1e___ps.pdf

jasa1063 wrote on 2022-09-11, 01:00:

Got this link with my post on this subject on vcfed.org to this Epson suipport bulletiin and it says you can use a Hercules card with the Epson Equity Ie.

https://files.support.epson.com/pdf/e1e___/e1e___ps.pdf

Thanks for clarifying and great that you found a confirmation that it can work rather than having to try it with hope and fingers crossed.

rmay635703 wrote on 2022-09-10, 17:42:

MDA works alongside any color adapter

Yes, but not MGA (aka HGC).

The Hercules Graphics Card has a so-called "Half Mode" in which one of the two graphics pages can be disabled.

The Hercuoes utility MSHERC for Microsoft products can be invoked by MSHERC /HALF for example.

If that's done, the HGC will coexist with a CGA card.
When in graphics mode, the HGC will disable (or not use) one of its two video pages, which would normally overlap with CGA.

That's why Hercules cards can emulate CGA, by the way - with the help of an utility (CGA emulator) and if no CGA card is installed.
It's not explicitly necessary to copy image data (which is slow also, but some CGA emulators do that
and re-format it for better image quality).

For a quick&dirty emulation, the CRTC is simply reprogrammed to accept CGA data at the default location.

If a Hercules card is configured properly, graphics output is possible simultaneously on both adapters (CGA, HGC).

MDA mode or textmode, which Hercules compatibles can provide as well, is 4 KB in size and located at a different address.
It won't conflict with EGA/VGA, so it can be used just fine. Not so the MGA mode.

PS: CGA has an addressing bug, by the way.
CGA's page size is 16 KB in size, but occupies a frame buffer twice (32 KB) the size.

MDA was in colour originally (true RGB output), but the feature was removed un later board designs.

MODE MONO or MODE CO40 or MODE CO80 from MS-DOS 4 and up will do have the same effect as a jumper on a PC/XTs motherboard.
They will tell the BIOS which adapter type is the primary, dominant adapter.

Back in the 80s, there existed utilities that did the same. In the fashion of MONO.COM or COLOR.COM etc.

Note that neither HGC nor CGA have a BIOS chip.
They're both Motorola CRTC based cards.
The PC BIOS merely supports CGA and the MDA portion of the MGA (MGA was the generic term for HGC).

I installed the both a generic MGA and STB Chauffer HT in the Epson Equity Ie. Trying to switch to the monochrome adapter for text output does not work. There is no BIOS support for a monochrome adapter in the Epson Equity Ie, which for me makes it a non-starter. I am just going to leave the computer with the MCGA adapter and go with that.