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Wanted: EGA card with internal monitor connector

RadRacer203

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Looking for a card that can do EGA, I just bought a GE Workmaster 1 (looks like a black IBM 5155 but almost completely different), so I'm looking for an EGA card with an internal header so I can have 16 colors on the original monitor. The monitor is identical to the one in an IBM 5155, so if it will work in one of those it will work in this too.
 

the3dfxdude

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Most EGA cards come with a feature connector header. Is that what you are looking for? What does the connector look like? I'm guessing it uses an RGB signal capable to 15khz/21khz horizontal. Because if it's any other specialty EGA thing, I think that will be hard to find.
 

Eudimorphodon

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The color subcarrier was not mixed in (see the text) as it results in patterning that degrades the monochrome image, but obviously you would need it for an internal color monitor.

Does the EGA card actually generate any colorburst/chroma signals to inject? If this portable actually does have a color composite monitor internally (that seems doubtful, though, 80 column text would be neigh-unreadable on it?) the most straightforward way to get color might be to build a DAC to convert the digital signal available on the feature adapter (like you did) into analog RGB and then look at the various RGB-to-composite encoder chips there are out there. But maybe I'm overestimating how hard it'd be to add chroma generation directly from the EGA signals.

(One of those converter chips would probably produce a composite output with colors true-er to the RGB colors than the mess IBM made of the CGA's color output...)

But the OP says it's the same monitor as the 5155, so I assume they mean 16 shades of gray?
 

the3dfxdude

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I have seen a CGA card from a 5155 or Compaq that has an internal composite port for this purpose. Is it a composite CRT then? It's what the 5155 had.
 

Hugo Holden

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Does the EGA card actually generate any colorburst/chroma signals to inject? If this portable actually does have a color composite monitor internally (that seems doubtful, though, 80 column text would be neigh-unreadable on it?) the most straightforward way to get color might be to build a DAC to convert the digital signal available on the feature adapter (like you did) into analog RGB and then look at the various RGB-to-composite encoder chips there are out there. But maybe I'm overestimating how hard it'd be to add chroma generation directly from the EGA signals.

(One of those converter chips would probably produce a composite output with colors true-er to the RGB colors than the mess IBM made of the CGA's color output...)

But the OP says it's the same monitor as the 5155, so I assume they mean 16 shades of gray?

Yes that confused me too, if the OP's question was actually to extract a color or a monochrome composite signal from the EGA card for a color or monochrome monitor in the computer. In other words is the monitor inside the computer that he wants to drive color, or monochrome ? If it is the same as the 5155 monitor, as stated, it is monochrome not color.

As noted in my article its easy for a monochrome monitor.

The color subcarrier is not too hard to generate from the signals on the EGA card, and you could use the same system of a few TTL IC's that exist on the CGA card to do it, these would have to be added to the feature adapter to get a composite color signal. Or, like you say, you could use a dedicated RGB to composite color encoder IC.
 

RadRacer203

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So it looks like I won't actually be needing a card. My goal was to get 16 colors (16 shades of amber) on the internal monitor of the Workmaster. It turns out an EGA Wonder I had at the bottom of one of my bins of parts did the trick. It just has the same internal header that the original IBM cga card did so it outputs composite through that. The EGA Wonder handles the colors and resolution so I should be able to run just about any graphics mode I want to on it.
 

Hugo Holden

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So it looks like I won't actually be needing a card. My goal was to get 16 colors (16 shades of amber) on the internal monitor of the Workmaster. It turns out an EGA Wonder I had at the bottom of one of my bins of parts did the trick. It just has the same internal header that the original IBM cga card did so it outputs composite through that. The EGA Wonder handles the colors and resolution so I should be able to run just about any graphics mode I want to on it.

I had heard that the EGA wonder card had the composite output already, though I have never owned one. The card EGA I use in my 5155 is the Video7 variety, and it needs the feature adapter to get composite video for the 5155's amber monitor. But I noted in the article, that with this system, only 15 shades of grey were possible displaying a CGA 16 color image (derived from a photo studio image) as composite monochrome, not 16. I wonder what the EGA wonder card does with that dilemma, they may have solved that. Still it displays 16 shades for any software you write for it.

Here is the remark from the article:

I found that a color level specified as 128 in PSP4 gave the low intensity colors and 255
initiated the high intensity colors. There was a problem specifying color 9 (grey = high
intensity black) because there is no unique combination of R, G and B colors in a .gif
image which is interpreted as this by the EGA card. This state is normally one of equal
R, G and B at a zero to low level but with the intensity signal on. So to get around this I
defaulted color 9 to be equal to color 8 in terms of the R, G and B level all equal and
specified as 128 each.
 
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Eudimorphodon

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ATI's 1980's video cards were wondrous creations. (As hinted at by the apropos name.) The resulting output wasn't always pretty to look at (they had to resort to horrifying tricks like interlaced and time-multiplexed dithering, etc.) but their ability to slap almost any video mode on any monitor was amazing.
 

ibmapc

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ATI's 1980's video cards were wondrous creations. (As hinted at by the apropos name.) The resulting output wasn't always pretty to look at (they had to resort to horrifying tricks like interlaced and time-multiplexed dithering, etc.) but their ability to slap almost any video mode on any monitor was amazing.

Actually, the ATI EGA Wonder, looks great on the 5155 amber monitor as long as you don't go above 640 x 200. What I believe is "Low Resolution EGA", 640x200x16 colors, looks fantastic on the 5155 amber monitors in different shades of amber. In fact, it looks much nicer than the CGA out put that is stock on the 5155. The attached photo is my own 5155 with an ATI EGA wonder showing output on the stock amber monitor and an LCD VGA monitor through an MCE2VGA Converter. That is 640x200x16 color mode playing Arkanoid. Click image to expand. The angle is a little extreme, so not the best example, but it looks fabulous!

portable1.jpg
 

Eudimorphodon

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Actually, the ATI EGA Wonder, looks great on the 5155 amber monitor as long as you don't go above 640 x 200. What I believe is "Low Resolution EGA", 640x200x16 colors, looks fantastic on the 5155 amber monitors in different shades of amber. In fact, it looks much nicer than the CGA out put that is stock on the 5155.

It's no surprise that looks fine, it's running a mode the monitor natively supports in terms of scan rates; it is when the EGA Wonder does stuff like mangling video modes to display on monitors that have the wrong number of lines that things get sketchy. (IE, turning on interlace to do 640x350 on CGA monitors or rapidly blinking colors/intensity signals on and off to fake more colors, or shades of grey on mono TTL monitors emulating color.)

I'm guessing the EGA wonder "knows" it's attached to a mono composite monitor and is therefore not sending it a chroma signal. That's why CGA usually looks terrible on mono composite monitors, the color information gets rendered as a bunch of stray dots/vertical stripes. Issuing a "mode bw80" at the DOS prompt "fixes" the problems in text mode (unless a program doesn't let the setting stick) by turning off the chroma signal/colorburst, but it's not a comprehensive fix, especially for CGA 4-color mode graphics. (I think it's technically possible to turn off colorburst in that mode? But I don't think most programs give you the option...)
 
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