AMD 64 bits: real frequency, FSB and multipliers
Athlon 64 of AMD as well function out of processor 32 bits as out of microprocessor 64 bits according to the operating system installed.
The socket 940 is replaced by the 939 for Athlon FX. The socket 754 is used for the bottom-of-the-range ones and manages one channel of memory (for 2 for the 940 and 939). For the opteron, speed indicated is fastest of the series.
The socket 940 requires registered memory, more expensive.