View Full Version : EGA on RGBS monitor?

April 10th, 2017, 12:13 AM
I got a 286, a commodore pc30-iii, that came with an ATI EGA Wonder card. I presume it is an ok card for a 286, but I have my setup all connected with RGBS. I have to admit I've never dabbled with EGA before and I'd prefer if I found a space for the computer that made it able to use its monitor and not on a shelf in my setup. But in case it goes into the setup - not that easy to figure out how it works from the pinout alone so instead of spending hours reading up on it I might ask someone who knows it well:


There is something about a 64 color EGA when using secondary colors. It is RGBi like CGA? Just with a mode that uses extra set of pins (on compatible displays I presume)? The monitor is a TVM MD-700, which I can't find anything on to know what it supports or not and if it is a good ega monitor or not. It sounds like it is easier just to replace the card with a VGA card and and run it through my vga to rgbs circuit.

I'm mostly collecting non-pc home computers, but I grew up with both an XT and a 486 so it is fun to remember those days too

April 11th, 2017, 11:55 AM
"It sounds like it is easier just to replace the card with a VGA card and and run it through my vga to rgbs circuit. "

Yes, that is considerably easier if you have the option.

EGA is 6 bit digital colour, it has RGB and then three intensity pins - one for each colour - RGBrgb etc. It is digital just like CGA but you can convert it to analog with a carefully chosen set of resistor ladders. However then you'll have to deal with the oddball sync rate which your monitor or upscaler may not be interested in. You'd also need to combine the HSync and VSync to generate a CSync for an RGBS display I believe.

April 11th, 2017, 12:34 PM
Not quite. Three intensity pins would imply that there are only two intensity levels for each color.

In fact, EGA encodes the intensity of each color as a two-bit number. 00 = off 01 = low 10 = medium 11 = high.

Thus there are 64 (4x4x4) possible color combinations. Not great, but better than CGA.

Back in the day (not that again!) I'd drive a workstation (Daisy) monitor with EGA output. The Daisy had 4 BNC connectors--I used an R-2R network to convert each color to an analog signal and then employed a XOR gate to combine the sync signals.

April 11th, 2017, 01:31 PM
Yeah, unless you already have an EGA monitor (or a CGA monitor and don't need high resolution or extra colors) it's much easier to just switch it out for a VGA clone.