iATKOS | United Kingdom

This is an Intel Core 2 Duo model with an ATI Radeon HD 4670 (256 MB VRAM) and 14 GB of RAM, but I have the exact same problem on a Core i5 from that year with an ATI Radeon HD 4850 (512 MB VRAM) and 24 GB of RAM.

They both have a High Sierra (native), a Catalina (DosDude-Patch) and a third partition for Big Sur (OCLP).

When I boot Big Sur, it starts fine, but after a while or maybe when I activate sth graphic "intensive" like the Launchpad or when I use Exposé with Hot Corners or run Freetube with a video, it starts glitching and then never stops again. The system becomes unusable and I have to reboot.

I know about limitations regarding non-Metal GPU's. But I don't have these glitches on other models with non-Metal GPU's on OCLP installs. (Of course, Maps e. g. is empty, but it won't start glitching.)

I read many posts here and nobody seems to have this problem (anymore). Apparently OCLP fixed certain glitches.

I used the latest patch program to install Big Sur. I even installed Monterey on the Core 2 Duo over Big Sur because I thought maybe that would fix it; it didn't.

Has it got to do with the fact that Dosdude's patch is running on another partition? (That changes some kexts, I understand.)

Apart from the fact that certain programs crash in Catalina and need to be started again immediately to work, Catalina runs well. Also High Sierra. No glitches.

(Well, actually Preview doesn't show graphics of some PDFs, strangely enough.)

I don't have these glitches on iMacs with smaller screens from different years.

I do have another iMac 27" from 2011, but I haven't tried to install OCLP so far.

Is there a fix to that?

Oh yeah, I did run the post install patches.