The highest speed -- no PR ratings here -- is currently 1.3GHz.
These also make very fine chips to bung into a dual AMD motherboard. Although AMD does not support this configuration, those looking for a cheap and cheerful combo could do worse than use these little almost "has been" chips.
They also have the advantage that unlike dual Via C3s, they're actually available right now.
But let us never forget what a sensible reader has pointed out to us.
A dual SMP system will not necessarily outrun a single processor system running at twice the clock speed.
And if you get fed up with noisy AMD chip fan noise, remember you can always underclock processors to cut down on the racket... µ