How am I getting EGA on my 5153 CGA Monitor?

Posted by pmodizzle@reddit | vintagecomputing | View on Reddit | 27 comments

I am not understanding what is happening here. Im working on an IBM 5170 AT that I got which came full of cards. The video card is an ATI VGA Wonder XL. I have been using it with a VGA monitor and all is well from that front. I had a CGA card from another machine that was giving me issues, so since I had the 5170 open I put the cga card in and tried it with my 5153 monitor. Worked fine, displaying all those glorious 4 colors of CGA. The ATI Wonder XL card also has a 9 pin connector on it in addition to the 15 pin VGA and a bus mouse connector. Out of curiosity I plugged the 5153 into it and it worked. I had gone into checkit and happened to look at system info, and it was showing up as EGA. Now out of curiosity I started trying some games in EGA mode - and they all work!?! Every one I tried in EGA. I know that a card like this has more vram than the original ibm cga card, and in certain instances graphics in 16 color can be displayed on a CGA monitor like this (PCJR comes to mind), but how is this working in what seems to be EGA with a CGA display?

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27 Comments

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BigRigChuckles@reddit

Simple explanation. CGA monitors support 16 colors, CGA does in fact have 16 color text mode. EGA is the same signal type and can do 16 color graphics on a a CGA display at 320x200 and 640x200, just don’t try to run software that utilizes the hi resolution 640x350 mode. (Unless you have an EGA card that supports interlacing to do so, ATi made an EGA wonder that could do 640x350 via interlacing on a 5153, that was in fact my setup with my first PC.)

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GerlingFAR@reddit

These monitors are so cool had one in the mid 90s. I connected red, blue, green, Vert and horizontal connectors as one connector and negative on the rest and I was able to turn the monitor into a black and white monitor connected to my VCR RCA output.

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irongear74@reddit

did u use any resistors? Or just connected it all and it worked? I am keen to try it :)

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GerlingFAR@reddit

I just straight connected them without a resistor at the time as I was experimenting with an old National VHS recorder I found back in the day.

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irongear74@reddit

ic. I tried it...didnt work for me :)

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lackystar@reddit

As texan said, it depends on the fact which EGA graphics mode you are using. As long as you use a graphic mode with only 200 lines like 640x200 or 320x200 (like in 99% of all EGA games) then it‘s possible to use a CGA monitor because in those graphic modes the horizontal sync is 15,75 kHz and that is the sync a CGA monitor is capable of. The other EGA graphic modes with more than 200 lines like 640x350 need a 21,85 kHz horizontal sync which the CGA is not capable of. Only EGA monitors can be driven with 15,75 kHz and 21,85 kHz. That‘s why you can run 99% of EGA games on a CGA monitor because they only use the 320x200 resolution. There are some games which use 640x350 resolution and these games cannot be run with a CGA monitor.

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pmodizzle@reddit (OP)

Very cool! I had no idea. This monitor also fits the AT better cosmetically than my PS/2 VGA one

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lackystar@reddit

You are right. This monitor fits cosmetically better with the AT because it‘s of this era. I mean the era of the IBM XTs and ATs. As mentioned before the CGA monitor was widely used in combination with an EGA card (in an AT). The EGA monitor was far too expensive so only the rich kids had one 😁

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c64z86@reddit

Sorry for replying to a late comment but I'm very interested in the early history of personal computing, so I have a question: Did people tend to skip EGA and instead went straight from CGA to VGA? Even on the IBM XTs? Was EGA not as popular as those 2 other standards?

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lackystar@reddit

Sorry that a long time I was not in Reddit. Just saw your question right now. Yes you are right a lot of people skip EGA completely as far as the monitor is concerned because the EGA monitors were very expensive. These prople instead upgrade the graphics card from CGA to EGA and used the EGA card with their old CGA monitors. This is why EGA monitors are very rare nowadays.

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Lectere@reddit

I've heard it before. If you have a EGA card you can display 16 colors on a CGA monitor

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Lectere@reddit

I have actually two original IBM CGA monitors. I don't know exactly what EGA card I should buy to make this work....

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texan01@reddit

any EGA card. I think I had a Paradise EGA card, or some other off-brand card I bought second hand.

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SaturnFive@reddit

Operation Neptuuuuuune!

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pmodizzle@reddit (OP)

You guys have all blown my mind, never knew a CGA monitor could do this. Also a pretty sweet video card for a system like this. VGA/EGA/CGA/MDA/Hercules all in one without even have to change dip switches. Retro enthusiast dream. Will have to try my 5151 with it and do some Hercules gaming.

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waydownindeep13_@reddit

Your thing is like PCjr or Tandy graphics with twice the resolution.. PCjr/Tandy is 16 colors at 320x200 for photorealistic image. This is 16 colors at 620x200 to make what is on your monitor no different than what you see in the real world. If you showed this to "normal" people, they would assume that this is footage your recorded from ESPN on your betamax machine.

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pmodizzle@reddit (OP)

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bd1308@reddit

Wait you could play operation Neptune on an AT?!

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Efficient-Sir-5040@reddit

The ATI VGA Wonder also did some internal downconversion on its own for some modes. Check the manual.

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bendalazzi@reddit

Fantastic choice of games!

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pmodizzle@reddit (OP)

Thanks. Obviously I favor the Sierra/Lucas arts adventure games. Operation Neptune is one that I use to test out a lot of systems. Not only was it nostalgic for me, but it’s graphically very nice, has adlib sound (don’t have an adlib compatible card in this machine yet), and it even runs decently on a 4.77 8088

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Distinct-Question-16@reddit

The sound of the ball moving is annoying

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texan01@reddit

You can display 16 colors on a CGA monitor at 640x200. The monitor doesn't care exactly what is driving it, either CGA or EGA, what it does care about is resolutions. and the max resolution is 640x200. If you try and drive it at 640x350, you'll get a sync failure and the display goes to old school static as it tries and fails to sync. You can damage it running it that high, so limit it to 640x200 resolutions. Back in the day, I was a poor Jr-high student and ran the CGA monitor with an EGA card for a long time.

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kbeast98@reddit

I had this monitor on my XT and i remember exactly this.

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Amazingprojectionist@reddit

This is correct

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tomxp411@reddit

Congratulations. You've discovered that EGA graphics cards are compatible with CGA monitors and, if the DIP switches are set correctly, will down-convert most display modes to 4-bit CGA. EGA cards were meant to be backward compatible, precisely because there were so many CGA monitors out there when the EGA card came out. Making it backward compatible made it easier for people to upgrade their old IBM PC and XT machines to EGA-equipped AT machines.

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glencanyon@reddit

I have a few EGA card manuals, and I was surprised to see that many of the EGA card could be used with an IBM Monochrome, CGA and EGA displays. [This is one that I uploaded the other day](https://archive.org/details/quadram-quad-ega-operations-manual-1985/page/n11/mode/2up) that mentions this.