The 500+ GFLOPS-producing monster chip is manufactured on a 80nm manufacturing process, which allows the chip maker to squeeze more transistors on the silicon.
While Nvidia was told by TSMC that the highest margin for 90nm process is 700 million, Nvidia pulled a wizard out of the hat and placed TMDS and HDCP logic on a separate chip. Sadly, the wizard also managed to break the NVIO1 chip, so you can forget about running 1080p video on your freshly-bought G80-based product.
ATI on the other hand, took the risky road, pulled 80nm manufacturing process from the drawing board onto silicon and produced a 720-million transistor monster that is currently seeking its final clock speed.
Regardless of the approach, in the end both products will be more similar than the companies are willing to admit. µ