I am writing a cross-platform OpenGL application and I am experiencing very different performance results between OS X and Windows (both 7 and 8).
In Windows GPU-Z reports the Sandy Bridge HD 3000 GPU continues to run at 350Mhz no matter what, and this would explain to me why my code seems to execute something like 5 times faster within OS X than in Windows.
To verify this, I thought it would be nice to verify that the clock speed is indeed getting ramped up in OS X but there is no GPU-Z for OS X.
Another way for me to put this issue to bed is to figure out how to get the IGP to correctly spool up under Windows. I have just tested sketchfab in Chrome, which has it hitting a nice full 1200Mhz on the TIE fighter model (and I was surprised at how well it scaled to GPU demand: less complex models had the clock set at 650 or 750Mhz. Pretty neat.)
Okay. So Chrome has something implemented right that I don't. Perhaps it's time I stopped using SDL. Now I've got to figure out how to get it to hit 1200Mhz when running my program.