16-Color CGA Commander Keen

SomeGuy

As some might know, Commander Keen 4 came in two flavors, one for 16-color EGA and one for ugly 4-color RGB CGA.

Well, some creative person came up with a mod that implements 16-colors on genuine CGA via CGA composite color artifacting.



It's pretty impressive, especially considering artifacting doesn't give you full control over what colors are where.

Different CGA cards can produce different artifacting colors, so this is optimized for genuine IBM CGA hardware. There does not seem to be a preference between the early and later (mono optimized) IBM CGA cards. I tried this on my PC clone and it looked very impressive. A little sluggish at 4.77mhz though. A V20 or a turbo XT might speed things up, but still it can run on stock IBM 5150/5160.

A page about it is on the Vogons forums:
https://www.vogons.org/viewtopic.php?t=48215

Technical descriptions here:
http://8088mph.blogspot.com/2016/05/dop ... een-4.html

And a video here:
https://www.youtube.com/watch?v=LJ_Fr7Ug7b4

ibmpc5150

This is nice patch for CGA composite.

I ordered both CGA and EGA version of Commnader Keen 4-5 from Apogee in 199x

Yes, CGA version was very hard to get with both media than EGA's one.

I played it on 486 PC with EGA graphic.

What purpose did I purchase it with CGA version?
It was only for collection, hehehe.

eli573

SomeGuy wrote:

Different CGA cards can produce different artifacting colors, so this is optimized for genuine IBM CGA hardware.

The CGA card does not, to my knowledge, effect the composite color artifacting. If it does effect the color artifacting, it would do it in either two ways.
1. No composite output, only RGBi
or
2. The image produced by one CGA card might be sharper or softer than the next, which might also alter the artifacting.
However, the colors of the artifacting will all be the same, unless if sharpness of output effects it. How NTSC handles color is to blame for this, and a different television set or composite monitor would likely effect the artifacting more than a different CGA card. This is why some CGA PC games were more colorful, but fuzzier, on a composite TV or monitor. Someone tell me if I'm wrong, it's been a while since I've looked into this; and if I am wrong, I apologize, especially for correcting someone with false information.

SomeGuy

Color artifacting was an undocumented byproduct of turning on the colorburst while the card is really in mono CGA mode. The resulting color is dependent on the internal timings of the card in that mode in relation to the composite color signal. Because this was undocumented, and only used by a few games, most clone cards do not really get it exactly right.

In fact IBM had two different revisions of the IBM CGA card - the later one was tweaked so no two "colors" would have the identical gray level on a monochrome composite monitor.

If you look at the recent 8088mph demo it starts off with a color selection for each version of the IBM CGA card and some extra adjustments.

On my Columbia Data Products clone CGA card, the color in that mode is off by somewhere around 180 degrees, but adjusting the hue makes it mostly viewable.

Supposedly this keen mod chooses a set of colors that look about the same on both IBM CGA models.