faster DDS clock

Assume a DAC being driven with an n-bit sine waveform at some clock
frequency, and then a lowpass filter and a comparator, generating a
programmable frequency clock.

Why not use both edges of the comparator output as our clock? That
de-stresses everything by 2:1, which could well be a net win on jitter
and such. Or gives twice the clock frequency with the same parts.