It's still in Beta and so far it's not currently making use of the CPU's as much as it could from whats being said on the FAH forums. There intending to get it to 100% at times but the threads seem to be jumping between the processors a bit.

Someone did set each thread affinity to each processor and said it made his times a bit faster but I cant remember how he did it. Or that much faster.

I've also read of people using the SMP client on a single core box fine at the minute...mainly because they couldn't get the 32 bit norma version to run...It worked and was completing units in about 1.6 days (within the deadline) but standford said that when the client comes out of beta, they maybe lowering the deadlines because after all, it's supposed to be a high performance client so it can speed up the results returning.

Maye give it a whirl on my single core to see what happens ;)