754 is an older AMD socket, which was released to replace skt A.
However, AMD decided it needed more pins for it's latest processors, so 939 is now the latest - replacement for 754.
754 will not be supported for very long, and will be phased out when 939 becomes cheaper.
939 works at whopping speeds, and can support AMD Athlon 64 X2's etc.
:-) Hope that helps.