It had some significant differences. Mainly the fixed SRAM render target. Fun fact is that a lot of tech from the 360 GPU made its way into Qualcomm Adreno GPUs. Reading about the tiled render pass OpenGL extensions in the Adreno was very reminiscent of working on the 360.

You’re right - I should have clarified that in my comment!

The Wii GPU is very much the GameCube one with some tweaks and faster clock speeds.

The 360 one is absolutely an ATI custom Radeon part.