As expensive as CGA monitors are, EGA monitors or even more expensive and difficult to come by. But did you know you could do EGA on a CGA monitor, albeit with some caveats? In this blog post, I’ll explain what degree of interoperability CGA and EGA have.
You can plug a CGA monitor into an EGA video card and it will work in text mode with no protest. This is useful for confirming an EGA card works even if you don’t have a proper EGA monitor. But EGA Mode 1 operates at 15 KHz and works just fine on a CGA monitor. That means you can plug a CGA monitor into an EGA card, and run EGA software as long as it confines itself to 320x200x16 or 640x200x16 resolutions, the two resolutions possible in Mode 1. It also means if you’re lucky enough to have an EGA monitor, it can do double duty and work with a CGA card.
Not all EGA software uses Mode 1, but enough does to make EGA on a CGA monitor somewhat useful. If the game uses 640×350 resolution, it will need an EGA monitor.
If you have an IBM EGA card, set DIP switches 1-3 to the OFF or OPEN position, and switch 4 to the ON or closed position. The switches on third-party EGA cards may vary.
Forcing EGA mode 1
Unfortunately, there is no universal method to force software into this mode. Some DOS software prompts you with questions when you launch it, asking what kind of display you have. It might also ask about your sound card. Others may have a configuration utility, but that was really more of a VGA-era thing. Still others will have command line switches to put them into EGA mode.
And in case you are wondering, EGA cannot emulate 16 color Plantronics or Tandy graphics. DOS-era systems didn’t have enough headroom for device driver trickery to make things like that possible. We take those kinds of things for granted today, but in the late 1980s, things were different.
All that said, a surprising number of games did just use EGA in 320×200 16 color mode. That’s because even though EGA couldn’t emulate Tandy graphics, it was much easier to create a set of graphics at 320×200 and then write software to support both standards than it was to create a 320×200 set and a 640×350 set.
And for software that actually did use the EGA modes beyond mode 1, you can run that software with a VGA card and VGA monitor.
For some people, that may be good enough. For others, it may only be an interim solution. But I think you’ll agree an interim solution is better than going without while you wait for an opportunity to acquire an EGA monitor to materialize.
David Farquhar is a computer security professional, entrepreneur, and author. He started his career as a part-time computer technician in 1994, worked his way up to system administrator by 1997, and has specialized in vulnerability management since 2013. He invests in real estate on the side and his hobbies include O gauge trains, baseball cards, and retro computers and video games. A University of Missouri graduate, he holds CISSP and Security+ certifications. He lives in St. Louis with his family.