Keen 4-6: Fix for choppy scrolling on certain EGA/VGA cards
Posted: Fri Jun 16, 2017 20:41
I'm not sure if this is the right place for this. I guess it should rather be posted on keenmodding.org, but I don't want to go through the hassle of creating a new account just for this.
I ran across a topic on the VOGONS forums called "Keen 4-5-6 choppy scrolling on EGA card". It was mentioned in the thread that Keen 4-6 have this issue, but Keen Dreams and BioMenace do not, so I assumed it would be possible to write a patch file for CKPatch to fix it. Further testing showed that the Keen 4 special demo doesn't have the scrolling issues on these cards, so I ended up using the code from that demo to patch the screen update code in Keen 4, 5 and 6. And it appears to work fine on these cards.
If you want to preserve the patch on keenmodding.org or extend the patch for other versions of Keen 4-6, or just want to try it on your old 286 (or whatever), feel free to do that. The patch files are attached to my post in the link above.
I ran across a topic on the VOGONS forums called "Keen 4-5-6 choppy scrolling on EGA card". It was mentioned in the thread that Keen 4-6 have this issue, but Keen Dreams and BioMenace do not, so I assumed it would be possible to write a patch file for CKPatch to fix it. Further testing showed that the Keen 4 special demo doesn't have the scrolling issues on these cards, so I ended up using the code from that demo to patch the screen update code in Keen 4, 5 and 6. And it appears to work fine on these cards.
If you want to preserve the patch on keenmodding.org or extend the patch for other versions of Keen 4-6, or just want to try it on your old 286 (or whatever), feel free to do that. The patch files are attached to my post in the link above.