AMD has begun shipping two new versions of its Athlon XP processor and says machines based on the chips can be expected in September.

The new Athlon XP chips have performance ratings of 2400+ and 2600+. In line with its aim to move measurement of performance away from megahertz and gigahertz, AMD did not release the clock speeds of the new chips. But PC Advisor can reveal that the 2600+ runs at 2.13GHz, while the 2400+ is rumoured to run at 2GHz.

The processors are built using AMD's 0.13-micron Thoroughbred core like the 2200+ processor, which was the first AMD chip to use the core and appeared in June this year.

The PC Advisor Test Centre has already completed performance tests on a 2600+ based system, and our findings show that the processor is "fast, very fast", according to reviews editor Will Head. He says that despite its lower clock speed the 2600+ is turning in results as fast as systems powered by Intel's as yet unannounced top-speed Pentium 4, rumoured to run at 2.8GHz.

For full reviews of PCs based on both AMD's 2600+ and Intel's still embargoed P4 see the November issue of PC Advisor out on 19 September.