Is a SAM considered a G2? I don't think so. It has something like 6 years of newer tech and faster(and much more) main memory than a Gamecube which was a G3.
Gekko has L2 cache and some SIMD instructions, both missing from the AMCC PPC440EP. While AMCC PPC440EP has some multimedia instructions they have little practical importance, while Gekko's SIMD is subset of altivec.
AMCC PPC440EP core is from 1999, same year as Gekko.
