Let's start by talking about the Athlon 64 X2 4200+. This CPU generally offers better performance than its direct competitor from Intel, the Pentium D 840. Most notably, the X2 4200+ doesn't share the Pentium D's relatively weak performance in single-threaded tasks like our 3D gaming benchmarks. The Athlon 64 X2 4200+ also consumes less power, at the system level, than the Pentium D 840—just a little bit at idle (even without Cool'n'Quiet) but over 100W under load. That's a very potent combo, all told.

In fact, the X2 4200+ frequently outperforms the Pentium Extreme Edition 840, which costs nearly twice as much. Thanks to its dual-core config, the X2 4200+ also embarrasses some expensive single-core processors, like the Athlon 64 FX-55 and the Pentium 4 Extreme Edition 3.73GHz. Personally, I don't think there's any reason to pay any more for a CPU than the $531 that AMD will be asking for the Athlon 64 X2 4200+.

If you must pay more for some reason, the Athlon 64 X2 4800+ will give you the best all-around performance we've ever seen from a "single" CPU. The X2 4800+ beats out the Pentium Extreme Edition 840 virtually across the board, even in tests that use four threads to take best advantage of the Extreme Edition 840's Hyper-Threading capabilities. The difference becomes even more pronounced in single-threaded applications, including games, where the Pentium XE 840 is near the bottom of the pack and the X2 4800+ is constantly near the top. The X2 4800+ also consumes considerably less power, both at idle and under load.