How does FSX perform with a high overclock of a single core in a multicore cpu (such as 3770K) - vs leaving all cores at stock speeds vs a mild overclock of all cores?

With the introduction of SP1, FSX was given the ability to use more than one core.  I think it works best when it has multiple cores all running at a high frequency.  When I switched from a dual core E6850 to a quad core Q9650, I did not see an increase in fps, but the sim was much smoother.  So I'd say you really do need at least four cores and run them all close to or beyond 4 GHz for optimum results.

Overclocking each core to different frequencies can be useful. For example if the max overclock you can handle is 4.7, because the hottest core is the limiting factor, then clocking that core a little lower can reduce temperatures enough to be viable.

 

I did try it once, but couldn't come to any definitive conclusions because I had a hardware issue to deal with, so had to abandon the experiment.