http://www.youtube.com/watch?v=Ms16uGxQzSY
At 31:00 you see the frame rate of 100ish on the top right, but if you look right next to it you see a completly different frame rate which is... you guessed it 45% lower! DAFUQ
Worthy of some suspicion, I'd say. On the other hand, I wouldn't assume there's shadiness afoot. That demo didn't have any details, like GPU, settings, how far along that Mantle build is, etc.
It's probably best to assume both numbers are one kind of bullshit or another and wait until it's in third-party hands.
A start time would help i dont whant to sit thru a hour of video to see what you are talking about....
31 minutes.
I've figured it out (actually someone on the Semi-Accurate forum spotted it). It's a crossfire setup. Over in the top-left corner it says "GPUs: 2", and the smaller framerate in the top-right is always half of the big number.