The reason I said R600 was a pretty scalable design is based on how it's progressed

Yeah they got rid of the ringbus and had to change things over time, but it's core design has evolved very very quickly

80nm 320SPs -> 55nm 320SPs -> 55nm 800SPs -> 40nm 1600SPs

All of this progressed VERY quickly while keeping die size down after the 80nm debacle

Yeah things changed along the way... more texture units, AA moved from shaders back to RBE's etc., but the architecture scaled very quickly

In hindsight, G80 started off more powerful than R600, but Nvidia has had a harder time scaling it up