When I first was playing around with SMP on an i7 920, I think I tried -smp 8 but was only getting like 40% CPU usage across the board, and eventually had to break it down into 4 clients running -smp 2, then tried -4 just now. Guess either I had done something wrong earlier, or F@H updated their stuff.
Check out Gomez Peer
on how to make your PC work for you. Referred by dark2099 please!
Mini Rig: Biostar TP67XE / i5 2500k / Corsair H55 / 2x4GB PNY / XFX 7770 / Corsair CX500M / Win 8 64 bit / Thermaltake V9 Blackwidow