2003-09-23 AMD Athlon 64 / 64 FX (Clawhammer) An "Opteron for the desktop", AMD64 (x86-64) chip previously known as Athlon DT or Clawhammer. Originally planned for October -02, later delayed to Q2, and launched in September -03 at Athlon 64 3200+ (2.0 GHz, $417), 3000+ ($278) and Athlon 64 FX-51 (2.2 GHz, $733).
Introduced with 1MB of L2 cache and two DDR channels in the 940 (later 939, incompatible to 940) pin package named FX.
The 754 pin package with only one DDR channel is the normal Athlon 64 and will be available with 1MB, 512KB and 256KB of L2 cache.
2004-06-01 AMD Newcastle AMD64 chip made in the 130 nm process with 512 KB of L2 cache. Will be available in both socket 754 and 939 versions (i.e single and dual channel memory controller). Athlon 64 FX-53, 3800+, 3700+ and 3500+ released.
BTW: The 939 socket is said to be invented as it makes it possible to build motherboards with fewer layers (and thus cheaper) than the 940 socket did.