Well, both the Wii and 360 projects were super secretive at ATI, so they may have actually gone any of many different ways with the final chip. But it's not the same part that's in the Gamecube. I'd have to get some more intel, but they may have done what they did for the retail R420 with it instead of basing the design on the then proposed R500 tech (which was removed as a retail project when these announcements were coming around).