good summary :-) Although Windows reports 50/50 for the two virtual processors its not an equal split. Hyperthreading is basically just using the wasted cycles caused by the overly long pipeline of the P4 (and even more for the newer Prescotts) and is more like 20~30%. So on a dual Xeon Vue 5 would still get at least 60% of the available CPU power and the remaining cycles would be used by the system and any other programs you have running, giving you a much more responsive PC. Athlon 64s (or Athlons) don't need hyperthreading as they have much shorter and more efficient pipelines so there would be very little to gain.