I just got a 12-core Mac Pro running OS X 10.7 (my first Mac! of course my work bought it) and hyperthreading is automatically enabled. I want to disable it to check performance changes on a program. I have looked everywhere for the additional preference panes but cannot find any of the old ones that used to exist in Developers/Extras. Any advice? For those interested: The program is the Burrow-Wheelers Aligner, and it is NEVER able to access the virtual cores. All outputs from both iStat and Activity Monitor indicating I am only using 50% (i.e. 600%) of total CPU, and all the virtuals are unused, so I want to disable and see if it will access 100% (i.e. 1200%) of CPU.