Barton and Thorton

Fifth-generation Athlon Barton-core processors released in early 2003 featured PR ratings of 2500+, 2600+, 2800+, 3000+, and 3200+. While not operating at higher clock rates than Thoroughbred-core processors, they earned their higher PR-rating by featuring a total of 512 KiB L2 cache and, in some models, a faster 400 MT/s front side bus.^[18] The Thorton core was a variant of the Barton with half of the L2 cache disabled and thus functionally identical to the Thoroughbred core.

By the time of Barton's release, the "Northwood" Pentium 4 had become more than competitive with AMD's processors.^[19] Unfortunately, due to the architecture of AMD's processor caches, an L2 cache increase to 512 KiB did not have nearly the same impact as it did to Intel's line. Only an increase of several percent was gained in per-clock performance.^[18] The PR rating became somewhat inaccurate because some Barton models with lower clock rate weren't consistently outperforming their higher-clocked Thoroughbred predecessors with lower ratings.^[19]

The other improvement, a higher 400 MT/s bus clock, helped Barton gain some more efficiency. However, it was clear by this time that Intel's quad-pumped bus was scaling well above AMD's double-pumped EV6 bus. The 800 MT/s Pentium 4 bus was well out of Athlon's reach. In order to reach the same bandwidth levels, the Athlon bus would have to be clocked at levels simply unreachable.^[18]

The K7 architecture had scaled to its limit. Maintaining performance equivalence with Intel's improving processors would require a significant redesign.^[18] AMD would soon launch Athlon 64.

Specifications:
Barton (130 nm)

• L1-Cache: 64 + 64 KiB (Data + Instructions)
• L2-Cache: 512 KiB, fullspeed
• MMX, 3DNow!, SSE
• Socket A (EV6)
• Front side bus: 166/200 MHz (333/400 MT/s)
• VCore: 1.65 V
• First release: February 10, 2003
• Clockrate: 1833-2333 MHz (2500+ to 3200+)
  • 166 MHz FSB: 1833-2333 MHz (2500+ to 3200+)
  • 200 MHz FSB: 2100, 2200 MHz (3000+, 3200+)

Thorton (130 nm)

• L1-Cache: 64 + 64 KiB (Data + Instructions)
• L2-Cache: 256 KiB, fullspeed
• MMX, 3DNow!, SSE
• Socket A (EV6)
• Front side bus: 133/166/200 MHz (266/333/400 MT/s)
• VCore: 1.5 V - 1.65 V
• First release: September 2003
• Clockrate: 1667-2200 MHz (2000+ to 3100+)
  • 133 MHz FSB: 1600 - 2133 MHz (2000+ to 2600+)
  • 166 MHz FSB: 2083 MHz (2600+)
  • 200 MHz FSB: 2200 MHz (3100+)