http://cube.ign.com/articles/100/100445p1.htmland
http://cube.ign.com/articles/100/100543p1.htmlare the two parts of an interview conducted with the engineers at IBM who designed the Gekko for the Gamecube.
It wouldn't surprise me at all if Broadway is an evolved Gekko, run on a 90nm process, with a larger cache, a higher clock speed, and possibly with two cores on the same silicon with an interface for dealing with it as a two core piece, or alternatively run as two seperate cores in a single package. Remember, the Gamecube was the best designed (arcitecture not visual style) system of the 6th Generation. I doubt that Nintendo will stray too far from it for the 7th Generation.
Here's another arcitecture article here:
http://www.eet.com/story/OEG20010516S0056As for the Hollywood GPU, I don't expect it to be derived from the flipper. It will be something new with a feature set that is a superset of the flipper features. The beauty part is that if we are dealing with a dual cpu, and the Flipper and the Hollywood have different instruction sets, the second CPU in the revolution can be used to transform Flipper instructions to Hollywood instructions, allowing fast and good backwards compatibility with the Gamecube.
I expect good things from the Revolution. I expect that it will support a much more rapid environment for code development than either of it's two closest competitors will be able to provide. The real hope and dream this generation involves whether or not Microsoft and Nintendo are able to keep Sony from taking a huge lead like it did in the 6th Generation.