PC Hardware in a Nutshell, 3rd Edition

Athlon 64

The Athlon 64 processor is based on the variant of the K8 core codenamed Clawhammer. The Athlon 64 supports 1- and 2-way operation, is due in September 2003, and is targeted at desktop systems. The Athlon 64 differs from the Opteron in the following important respects:

HyperTransport Technology channels

Rather than the three HTT channels used by the Opteron, the Athlon 64 has only one HTT channel.

Memory controller

Rather than the 144-bit dual-channel DDR333 ECC memory controller used by the Opteron, the Athlon 64 has a 64-bit single-channel DDR333 non-ECC memory controller. (Shipping models may include DDR400 support.) The narrower memory interface of the Athlon 64 means its memory bandwidth is half that of the Opteron. Like the Opteron, the Athlon 64 integrates the memory controller onto the processor.

Cache size

The Athlon 64 and Opteron both have the AMD-standard 128 KB L1 cache, with 64 KB allocated to instructions and 64 KB to data. Opteron processors provide 1 MB of L2 cache. Athlon 64 processors are available with either 256 KB or 1 MB L2 cache. Our moles tell us that for performance reasons, AMD may decide to ship the “small” Athlon 64 with 512 KB L2 cache rather than 256 KB.

Chipset support

Most Opteron systems will be built around the server-class AMD 8000-series chipset. Most Athlon 64 systems will use desktop-class chipsets such as the nVIDIA nForce3, the VIA K8T800/K8M800, and others. Based on our experiences with the nForce and nForce2 Athlon chipsets, we expect ...