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A strange hidden feature of the IBM MDA card...

ejs said:
It's just a QBASIC program with PRINT statements and COLOR fg, bg statements. You could hack something up in a few seconds.

If you want the "MDA" artwork at the end, I've attached it here as a BSAVE image.

View attachment 43195

From QBASIC, do this:
Code: 
DEF SEG = &HB000
BLOAD "MDA.BIN", 0

It should also work on a standard CGA card, just use &HB800 instead of &HB000.
Click to expand...

Could you take a picture of the tracks you wired ? Because I am following the schematics and the pin 6 should have come from U64:12 but its not the case, I have it on U64:9 and pin 7 from U64:7 instead of U64:5. Are you pulling them straight from U30 ?
 
ejs said:
It's just a QBASIC program with PRINT statements and COLOR fg, bg statements. You could hack something up in a few seconds.

If you want the "MDA" artwork at the end, I've attached it here as a BSAVE image.

View attachment 43195

From QBASIC, do this:
Code: 
DEF SEG = &HB000
BLOAD "MDA.BIN", 0

It should also work on a standard CGA card, just use &HB800 instead of &HB000.
Click to expand...
Wait, you didn't have to tweak the video processor settings?

Are you saying it just normally outputs color video all the time, except A: Normal mono programs don't write color attributes, and B: The sync and resolution is not compatible with "standard" TV-resolution RGB monitors, therefor requiring a Multisync or similar?
 
Oh I think I found it you connect missing U30 to U63 and missing U63 to U64.

The pins were correct there are resistors in the middle my bad :p
 
SomeGuy said:
Wait, you didn't have to tweak the video processor settings?

Are you saying it just normally outputs color video all the time, except A: Normal mono programs don't write color attributes, and B: The sync and resolution is not compatible with "standard" TV-resolution RGB monitors, therefor requiring a Multisync or similar?
Click to expand...

Yep! As long as you have an early MDA card and a multisync monitor, it just works. However, programs that "play nice" will see that you've set the monochrome switch and not generate color attributes.
 
The later Tandy 1000s will output MDA/Hercules video on the green pin as well as the normal pin 7 monochrome video output. This allows you to almost successfully display MDA on a CGA monitor if you tweak the controls far enough (as shown below). I wonder if these also have latent "color MDA" capability?

mda_on_cga1.jpg
 
ejs said:
Yep! As long as you have an early MDA card and a multisync monitor, it just works. However, programs that "play nice" will see that you've set the monochrome switch and not generate color attributes.
Click to expand...

I wonder if you multisync interprets the signal as EGA (thus 6-bit) or CGA-like RGBI. Because if it was EGA the colors will be off. Can you draw a colorbar ?
 
SomeGuy said:
Are we talking about having to add wires to the original version, or just the later version?
Click to expand...

he is talking about adding the wires to the later version (the early doesn't need them).

Connect all missing lines for R, G and B across U30, U63, U64 and the DB9

Going to mod mine this weekend.
 
Okay I had to this, but since I don't have a multisync, I had to add color support to my MCE2VGA:

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What do you mean by stable ? The signal ? My MDA seems to have the clock a little off so I get some noise in the left and right...

But anyway MDA is just for the curiosity :D
 
Retro Canada said:
I wonder if you multisync interprets the signal as EGA (thus 6-bit) or CGA-like RGBI. Because if it was EGA the colors will be off. Can you draw a colorbar ?
Click to expand...

It's definitely CGA-like RGBI. I played around with the colors and everything was a match, including brown. It worked fine in NEC's "auto" digital mode, but I also tried forcing it to 16 color mode (it has jumpers for 8, 16, and 64 colors for manual mode).
 
ejs said:
It's definitely CGA-like RGBI. I played around with the colors and everything was a match, including brown. It worked fine in NEC's "auto" digital mode, but I also tried forcing it to 16 color mode (it has jumpers for 8, 16, and 64 colors for manual mode).
Click to expand...

Which model NEC monitor are you using? I have a JC-1401P3A. I don't have a manual for it and don't know if it could be hooked up with a straight through DB9 cable to an MDA, CGA, or EGA display adapter, and how all of the various switches would need to be set.
 
Sorry for a bit offtopic, but if CGA card contains Color/Mono switch, does it mean it contains MDA and CGA? Is it offering real MDA or is it just CGA converted into single color? MDA outputs green color?

If it's MDA, does it make contradiction to IBM 5150's motherboard switch settings? I would like to have both CGA and MDA but I like the idea that I could switch between them without need to open the case each time and set the motherboard's switches manually.
 
musicforlife said:
Sorry for a bit offtopic, but if CGA card contains Color/Mono switch, does it mean it contains MDA and CGA? Is it offering real MDA or is it just CGA converted into single color? MDA outputs green color?
Click to expand...
It depends on the card. If it has a composite video output, then switching it to mono mode probably just kills the color burst, so it's likely to be CGA-only.

If it's MDA, does it make contradiction to IBM 5150's motherboard switch settings? I would like to have both CGA and MDA but I like the idea that I could switch between them without need to open the case each time and set the motherboard's switches manually.
Click to expand...
It is possible to have both CGA and MDA cards installed. The motherboard jumpers just determine which one is the primary display. Once booted, you can switch between them or even use both at the same time -- as CAD programs often did, to display graphics on the color display and text commands on the monochrome display.
 
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