I actually don’t know the answer to either of these questions. As far as I know the black cubes show up on both the 32 and 64 bit clients in dx11 mode (I might check when I get home), so I think it’s just a DX11 thing.
I’m not suuuper-concerned about the CPU usage as long as it’s still functional. I have to pick my battles on linux patches since it’s not officially supported so I work on it in my spare time. I’ll keep an eye on the situation but I won’t be putting any time into investigations unless CPU usage makes it impossible to play. I am however always open to people who know what’s up telling me what’s wrong and giving me clear info on how to fix it, so if you know why it’s happening please clue me in