The difference between new and older CPUs is pretty easy to explain. Older microarchitectures have 64-bit mmx/sse execution units and split 128bit sse ops into 2 64bit microops. Newer archs have 128bit sse units.
- AMD K8: 2 64bit units
- intel Core/Core2: 3 64bit units
- AMD K10: 2 128bit units
- intel nehalem: 3 128bit units K10 = Opterons with 4 or more cores, Phenom, Phenom II, Athlon II nehalem = xeon 34xx/35xx/36xx/55xx/56xx/65xx/75xx, i3/i5/i7