theortically the 650 isnt supposed to do any better than the 600.
individual mileage will vary: some have 600@1200, some 700@850.
i guess its all luck (and the quality of your chip)
now the reason why the 650 is no more than the 600 is because the 650 still uses
the 1.5v default, the only diff. is the 6.5 multiplier, vs 600's 6.
