Will, I'm no expert, but wanted to write about my experience with this in case it helps. I had the same problem with AMD dual core. When you talk @ the AMD Dual core optimizer, I assume you're trying one of the optimized builds at http://redump.emubase.de/mame.php ? I tried both of the AMD optimized builds (Athlon XP & 64), and the Athlon XP worked just fine. Perfection - no more stuttering frames or sound. I don't know that this build leverages the full processor cycles for 2 threads, but it seems to perform as well or better than my p4 3GHz w/ HT with MAME. I read several posts elsewhere in the MAME community with advice on changing drivers, turning off the "cool 'n quiet" technology, etc. Using the Athlon optimised build was the only solution that worked straight away. Good Luck!