You can run the burn in at 100% and it will run the CPU's at 100%, but it's not going to do anything with the GPU's. 3DMark has priority over the CPU burn on the first core, so when I run 3DMark, the duty of core 1 is reduced. 3DMark runs like crap, but it runs. And the CPU load is still 100% (3DMark using what it can with the burn in using whatever's left.)