they have made socket 939 just to accomodate both FX series and 64 series processors.
last processor in 754 pins is 3700+ and this is only one coming with 1MB L2 Cache, else all others are 512K. and I believe they wont make any more on this pin.
difference between FX and 64 series is the memory controller being 128-Bit in FX and 64-Bit in 64 series. in other words, FX series is built on Server CPU Optron core.
Intel Core2Quad 2.66Ghz 12MB L2-Cache
4096MB DDR Kingston Hyper-X
XFX 9600GT AlphaDog
Seagate 2 X 320GB SATA2
LG L246WH Flatron 24"