The P4 was just a waste. It was slower (at the same clockspeed) than its predecessor pIII. It used more power. The Athlons easily let it bite the dust (?), having a significantly higher IPC. The Core2 architecture has an IPC (instructions per cycle) higher than the A64, making it absolutely superior to the P4. If it really is a 50% increase in performance is doubtable, but certainly not impossible in certain scenarios. Quake 4 actually does support multithreading, so it's not an ideal basis for comparing a single core P4 to a C2D. Take a Pentium D, for example, to compare it to a C2D.