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The first series of MDA adaptors for the IBM PC had the ability to show colours according to the attribute byte, much like the CGA does in text mode, but I don't remember any PC application that supported colour display on MDA.

Tommy found a modern (2018) demo by TubeTimeUS showing off with MDA colour output.

The question is not about accidentally, but explicit support. I would imagine that an application doing so would need to offer configuration settings for this usage, as there was no way to detect if the MDA is for one connected to a colour screen and equally important capable to do so, as later versions dropped that feature.

Beside setup, disabling blink mode to support background intensity instead might be another criteria to look for.


Background:

A recent question about graphic base addresses made me look into IBM's Technical Reference for the PC and remember that the original MDA had the ability to output colour. This is nicely visible on its schematics:

Sheet 9 of the MDA Schematics on page D-20 of the August 1981 Technical Reference, showing he forwarding of the attribute byte for fore/background as colours to the display connector

(Sheet 9 of the MDA Schematics on page D-20 of the August 1981 Technical Reference)

It's also in part documented in chapter 2 by using the letters R/G/B to mark the bits for fore and background, but does not elaborate any further:

Description of the attribute byte on p.2-40 of the August 1981 Technical Reference (Description of the attribute byte on p.2-40 of the August 1981 Technical Reference)

Encoding is the same as for CGA in text mode, and connecting an MDA to a CGA screen will produce colours as fine.

In the 1983 edition those connections are gone, while the description stays the same:

Sheet 7 of the MDA Schematics on page D-42 of the April 1983 showing no connection for the colour signals

(Sheet 7 of the MDA Schematics on page D-42 of the April 1983)

All chips are still there, so it might be possible to reenable this.

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  • 1
    It doesn't provide an answer to the question, but noting that youtube.com/watch?v=-TiHFWH4NWk purports to be the output of a short colour MDA demo (i.e. not an application), in case there's any dispute.
    – Tommy
    Feb 7 at 15:14
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    @manassehkatz-Moving2Codidact Sure. Text is what MDA is about. And coloured is a nice add on. Just think how much Norton Commander or other text UI gained from using colour. Also, reasonable priced is relative. The very reason why many Apple II users only had green screens, despite it supporting colour.
    – Raffzahn
    Feb 7 at 15:15
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    @Tommy Nice find. I will add that if I may.
    – Raffzahn
    Feb 7 at 15:17
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    @manassehkatz-Moving2Codidact The CRTC could be reprogrammed for other formats, and there are remains of supporting more than one format in the design (software selectable pixel clock and horizontal resolution, but only one clock available), and jumper JP1 to invert VSYNC polarity, control underline feature, and select another font from the chargen ROM. Incidentally, same chargen ROM was used in CGA. Colour text out from early MDA has been demonstrated in a Youtube video.
    – Justme
    Feb 7 at 15:20
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    @Justme That's of course always possible - much like the CGA's famous 160x100 mode. MDA might do essentially the same as 160x175. But as mentioned, using graphic symbols with colour support goes already a long way.
    – Raffzahn
    Feb 7 at 15:27

1 Answer 1

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I don't think so, no, because the MDA card could only connect to mono displays at that time.

The monitor connectors use different pins, as shown here:

MDA: https://www.seasip.info/VintagePC/mda.html

CGA: https://www.seasip.info/VintagePC/cga.html

You can't connect a CGA display to an MDA card, or vice versa. https://www.vogons.org/viewtopic.php?t=69136

So even if it were possible, contemporary screens couldn't do it.

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  • The different pinouts, etc. for MDA vs. CGA was deliberate by IBM. But there were other monitors, not made by IBM and plenty of people used them. Eventually these include monitors that could connect to a variety of different video cards with very different modes, such as the classic NEC Multisync. "contemporary" screens included a lot more than the two monitors offered by IBM. May 9 at 17:59
  • @manassehkatz-Moving2Codidact This is true but only partial because it lacks important context. Yes, later, multiple other monitor standards appeared, and monitors appeared that could connect to more than one at once. But this happened in part because CGA was superseded by EGA, which was later superseded by VGA. MDA was replaced by Hercules, and then it was replaced by these newer, better standards. But not in the era of CGA and MDA. May 11 at 12:08
  • MDA was not replaced by Hercules. Hercules used the same exact monitors and, as I understand it, so close to the same timing, signals, etc. that for all practical purposes it was the same at the output as MDA (except perhaps this question of possible color) - the difference was on the computer side where it could produce graphics instead of just text. But yes, the true "Multisync" monitors came from a perceived need for a single monitor that could connect to multiple signal types. Not "more than one at once" - that was a later innovation, though common with today's LCD monitors. May 12 at 1:33
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    I think you are taking the most literal possible interpretation of my answers. I was there at the time. I supported this stuff in production environments. When I say "replaced" I mean replaced in the market -- as in, as PC compatibles sold, plain text-only displays were quickly replaced in product ranges by Hercules. "Connect to more than one at once" means "without different cables, adapters or changing settings", not "simultaneously". I was trying to be terse due to comment size limits on this site. May 15 at 12:01

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