and specifically, a FULL+ PPC chip as opposed to Xenos or Cell...
The Gamecube's was a full PPC G3 with a faster bus (up to 200MHz), extra cache (and programmable), 37 SIMD (ala Altivec) instructions and 2 32bit interger math processors replacing 1 64 bit one. "Broadway" is 100% backwards compatible with the "Gekko".