http://www.linuxquestions.org – I was looking around on Wikipedia, and ran across the UltraSPARC T2 processor. This is a processor with 8 cores (8 physical processors) and 8 threads per core (64 logical processors!) I'm aware of Intel's Hyper-Threading and other technologies, and I know collisions between the threads have the possibility of decreasing the processor's throughput. (HowTos)