Multicore should not be too much of a problem because sims parallelize well.
The random number generator (RNG) is a non-issue. If you want to do 10,000 iterations then you can do 2500 iterations on each core of a quad-core processor. No "live" data need be shared among the threads, as the only shared state is the initial board, bag and racks, which is read-only. Each thread keeps a local copy of everything it needs. Each RNG is independently seeded. The only point I'd make is: if Quackle uses a GADDAG normally, then we might want to consider using a DAWG instead. A B3 stepping Phenom/Barcelona quad-core processor has 512KB of L2 cache per core. A DAWG just barely fits into that. A GADDAG won't fit, and the GADDAG won't even fully fit into the 2MB L3 cache. Other processors will have similar limitations, but a quad-core Opteron is about the strongest thing we can expect to see on a home user's desk. It would be interesting to benchmark various processors on Scrabble sims. The Phenom doesn't scale very well in press reviews compared to the 3.2GHz Athlon64x2.
