Gecko's CPU Library

AMD Athlon (Thunderbird) processors

Introduction: June 2000


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 Thunderbird core

The second generation Athlon, the Thunderbird, debuted on June 5, 2000. This version of the Athlon shipped in a more traditional pin-grid array (PGA) format that plugged into a socket (Socket A) on the motherboard. It was sold at speeds ranging from 700 to 1400MHz. The major difference, however, was cache design. Just as Intel had done when they replaced the old Katmai Pentium III with the much faster Coppermine P-III, AMD replaced the 512KB external reduced-speed cache of the Athlon Classic with 256KB of on-chip, full-speed cache. As a general rule, more cache improves performance, but faster cache improves it further still.

AMD changed cache design significantly with Thunderbird. With the older Athlon CPUs, the CPU caching was of an inclusive design where data from the L1 is duplicated in the L2 cache. Thunderbird moved to an exclusive design where the L1 cache's contents are not duplicated in the L2. This increases total cache size of the processor and effectively makes caching behave as if there is a very large L1 cache with a slower region (the L2) and a very fast region (the L1). Because of Athlon's very large L1 cache and the exclusive design which turns the L2 cache into basically a "victim cache", the need for high L2 performance and size was lessened. AMD kept the 64-bit L2 cache data bus from the older Athlons, as a result, and allowed it to have a relatively high latency. A simpler L2 cache reduced the possibility of the L2 cache causing clock scaling and yield issues. Still, instead of the 2-way associative scheme used in older Athlons, Thunderbird did move to a more efficient 16-way associative layout.

The Thunderbird was AMD's most successful product since the Am386DX-40 ten years earlier. Mainboard designs had improved considerably by this time, and the initial trickle of Athlon mainboard makers had swollen to include every major manufacturer. Their new fab in Dresden came on-line, allowing further production increases, and the process technology was improved by a switch to copper interconnects. In October 2000 the Athlon "C" was introduced, raising the mainboard front side bus speed to 266MT/s (133MHz double-pumped) and providing roughly 10% extra performance per clock over the "B" model Thunderbird.

Source: Wikipedia, the free encyclopedia.