Thanks ejrolon, I read Ars every day yet somehow managed to miss that one.
The problem was 'fixed' in that Apple swapped to NVIDIA cards as the default graphics card. The problem with the ATI cards was not limited to iMacs .. my old firm had a whole batch of new Mac Pros suffering the same problem until we got the cards switched to NVIDIA. This must be pretty embarrassing for Apple to have the same problem again. I wonder why they even offer the ATI cards as an 'upgrade' option when they must know they have heat issues (surely they do some heavy stress testing internally).
Design Technology Manager
| francis-jones morehen thorp
iMac 27" i7 2.93Ghz | 32GB RAM | OS 10.10 | Since AC5