Gecko's CPU Library

AMD Athlon XP/MP (Barton, Thorton) processors

Introduction: February 2003 (Barton), September 2003 (Thorton)


Athlon was the brand name applied to a series of different x86 processors designed and manufactured by AMD. The original Athlon, or Athlon Classic, was the first seventh-generation x86 processor and, in a first, retained the initial performance lead it had over Intel's competing processors for a significant period of time. AMD had continued the Athlon name with the Athlon 64, an eighth-generation processor featuring AMD64 (later renamed x86-64) technology.

Athlon was the ancient Greek word for "Champion/trophy of the games", and made its debut on June 23, 1999.

The Barton and Thorton cores

Fifth-generation Athlon Barton-core processors released in early 2003 featured PR ratings of 2500+, 2600+, 2800+, 3000+, and 3200+. While not faster than Thoroughbred core processors in clock speed, they earned their higher PR-rating-per-clock by featuring an additional 256KB of full-speed on-chip level 2 cache, for a total of 512KB, and a faster FSB. The Thorton core was a variant of the Barton with half of the L2 cache disabled and thus functionally identical to the Thoroughbred-B core. The disabled L2 cache on some Thortons was partially defective, but on others it could be re-enabled through bridge modifications.

As with most Athlons, the Barton core was popular with overclockers. For example, the 2500+ was rated to run an a 333MT/s (166MHz double-pumped) bus. By increasing this to 400MT/s (200MHz double-pumped), it became equivalent to the much more expensive 3200+. Some suspect this was the reason for the relatively short retail lifespan of the lower-rated Bartons, which were the first to be replaced by the cut-down Semprons.

Some AMD proponents claimed that these new parts regained performance leadership for the Athlon, but this remained in doubt. Much controversy surrounded the benchmarks which are used to measure performance leadership. In particular, industry insiders pointed out that some tests had been deliberately skewed in Intel's favour - notably the BAPCo tests, which were written by Intel's own engineers. Other insiders accused AMD's model numbers of no longer being internally consistent, and also accused them of basing their processor ratings on applications which were no longer widely used.

Most observers considered the Athlon no longer the fastest x86 processor in the world, believing that Intel's Pentium 4 overtook the Athlon XP early in 2002 and held its lead until February 2003, with the 3.06GHz P4 benchmarking slightly faster than the Athlon 2700+. At the time, the question was moot: AMD had yet to deliver the 2700+ and 2800+ in commercial quantities; they did not begin to ship in volume until well into the first quarter of 2003. However, as the initially troublesome transition to the 0.13 micrometre process neared completion, AMD began producing large numbers of 0.13 micrometre parts in the 1700+ to 2400+ speed grades (usually a sign that faster grades are not far away). In mid February 2003, they announced the Athlon XP 3000+ to ship in volume in early March of 2003. Pending an Intel reply, the 3000+ had according to AMD reclaimed the "fastest x86 in the world" title for the Athlon once again. However, reviewers' opinions on this were split, and most still believed the top Intel part to be faster. A month later, Intel introduced a new series of Pentium 4s which had a faster 800MT/s, or 200MHz quad-pumped bus (previously it was 533MT/s, or 133MHz quad-pumped. The new bus was indicated by the "C" appendage at the end of the model number) and support for Hyper-Threading. In response, AMD released the Athlon XP 3000+ and 3200+ featuring a 400MT/s bus. Unfortunately, the bus speed increase did not offer a large performance gain. The 3200+ failed to outperform convincingly the new 3.0GHz Pentium 4 'C', much less the subsequent 3.2GHz version. Many reviewers concluded that the C-series Pentium 4 was a bridge too far for the Athlon XP, and that Intel had gained a decisive performance lead which the Athlon XP could not overcome. However, AMD did not try to do so; their focus was now on the soon-to-be released K8, the Athlon 64.

Source: Wikipedia, the free encyclopedia.