500 MHz of pure love..

The r500 chip is running at 500 MHz speeds- this helps Developers meeting a october/november luanch.
Microsoft says this is the final clock speed of the chip, but there are reports that the chip can go higher- if this is true expect the Developers of the 360 to have the ablilty to do some serious overclocking.
Playstation 3's RSX GPU eveloped by Nvidia is said to run at speeds of 550 MHz. Its skeptical for people to say "hey, the number is bigger- so its better."
this isnt always true. The xbox 360's archtechture is "unified" unlike the PS3's design. The 360 might very well be the power house of the next generation.