Source: AMD website.
The Athlon64 and its bigger brother Athlon64 FX have been around for over a year. They have since become that much more attractive with the release of Socket 939. Now, the most important difference with the Opteron's Socket 940 is that no registered memory is required. Also, while Socket 754 only supports 64 Bit single channel DDR400 memory, Socket 939 Athlon64 processors run in 128 bit dual channel mode. The integrated memory interface is, in fact, one of the most important architectural keys that unlocks the Socket 939 Athlon64's performance.
Here is a quick comparison of all processors:
|Athlon64||3000+||2.0 GHz||512 kB||754||$ 173|
|Athlon64||3000+||1.8 GHz||512 kB||939||$ 173|
|Athlon64||3200+||2.0 GHz||1 MB||754||$ 227|
|Athlon64||3200+||2.0 GHz||512 kB||939||$ 227|
|Athlon64||3400+||2.2 GHz||512 kB||754||$ 288|
|Athlon64||3500+||2.2 GHz||512 kB||939||$ 346|
|Athlon64||3700+||2.4 GHz||1 MB||754||$ 507|
|Athlon64||3800+||2.4 GHz||512 kB||939||$ 643|
|Athlon64||4000+||2.4 GHz||1 MB||939||$ 729|
|Athlon64||FX-53||2.4 GHz||1 MB||939||$ 729*|
|Athlon64||FX-55||2.6 GHZ||1 MB||939||$ 827|
|*will be phased out soon|
All the basic information around AMD64 and the Athlon64 processors can be found here: