AMD has released what it says is the highest-performance processor ever, strictly for "enthusiasts and hard-core gamers".

The Athlon 64 FX-55 and the Athlon 64 4000+ will take over the top of AMD's performance lineup. The Athlon 64 FX product line is for the most demanding users and applications, while the Athlon 64 is a more mainstream chip for the consumer and business desktop market.

The Athlon 64 FX-55 runs at 2.6GHz and matches up against Intel's Pentium 4 Extreme Edition processor - its highest-performance chip. Both come at a premium. The Athlon 64 FX-55 costs $827 in quantities of 1,000 units; the 3.4GHz Pentium 4 Extreme Edition costs $999, in quantities of 1,000.

Most AMD users and large PC vendors prefer the cheaper Athlon 64 processor. In order to increase performance over the Athlon 64 3800+, AMD added 512KB of cache memory to the Athlon 64 4000+ for a total of 1MB of Level 2 cache.

The Athlon 64 4000+ is virtually identical to the Athlon 64 FX-55, but runs slightly slower at 2.4GHz and is less expensive at $729 in quantities of 1,000 units.

AMD expects to have the performance lead among mainstream desktop PC processors with the Athlon 64 4000+, said Jonathan Seckler, product manager for the Athlon 64 product line. Industry analyst Nathan Brookwood agreed, especially in the near term as Intel resets its road maps. "For some folks who are really pushing hard on performance and for whom seeing an hourglass is an economic or emotional kind of problem, AMD will have an advantage," said Brookwood, of Insight 64.