Thunderbird (T-Bird)

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 also shipped in the slot A package). It was sold at speeds ranging from 600 to 1400 MHz. 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 512 KiB external reduced-speed cache of the Athlon Classic with 256 KiB of on-chip, full-speed exclusive cache. As a general rule, more cache improves performance, but faster cache improves it further still.^[11]

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).^[12] 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.^[11]

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 133 MHz (266 MT/s) and providing roughly 10% extra performance per clock over the "B" model Thunderbird.

Specifications

• L1-Cache: 64 + 64 KiB (Data + Instructions)
• L2-Cache: 256 KiB, fullspeed
• MMX, 3DNow!
• Slot A & Socket A (EV6)
• Front side bus: 100 MHz (Slot-A, B-models), 133 MHz (C-models) (200, 266 MT/s)
• VCore: 1.7 V - 1.75 V
• First release: June 5, 2000
• Clockrate:
  • Slot A: 650 - 1000 MHz
  • Socket A, 100 MHz FSB (B-models): 600 - 1400 MHz
  • Socket A, 133 MHz FSB (C-models): 1000 - 1400 MHz