I read that M290X is basically a desktop HD 7870 but with lower clock speed. Notebookcheck.net says: "The M290X in particular is similar to its desktop Radeon HD 7870 counterpart with 1280 1D shader cores and 80 texture units, but has a core clock of only 900 MHz (boost) versus the 1000 MHz clock of the HD 7870" AMDs website confirms these specs for both cards. However, I checked both cpu-z and gpu-z and they both display a 975Mhz clock and even a higher memory clock 1365Mhz on M290X vs 1200 on 7870. Could it be that the M290X in the iMac is overclocked compared to the reference specs and is, in fact, equal in performance to desktop 7870? I am asking because Witcher 3 cites HD 7870 as a minimum requirement to play, so I'm wondering if I'll be able to run it in 1080p As I mentioned in one post, I did not get the iMac to play games, but Witcher is something I'd love to try out.