You might examine other possibilities as well. One big one is if you have a Pentium 4 processor. I've been fighting with CPU spikes in PD for a very long time now, and often find them related to denormal numbers. These are numbers very close to absolute zero, but not quite there, and are characterized by an extremely long series of digits after the decimal point, and which kick a P4 CPU into extremely slow and accurate mode. I found the problem to be much worse under Linux, but that doesn't mean it doesn't exist under windoze.
So, i've read some of the previous postings on this, and it surely sounds like that has happened to me. I read a tip about adding noise to critical sections of the patch, but can't really figure out how much and in what kind of situations. It would be great to see a patch which does this.
one possibility is to add noise of about 1e-10 ... also the PD_BADFLOAT macro that's supposed to flush denormal numbers to zero ... but it's only killing numbers that are already denormals... i'd suggest to use the devel_0_37 branch since it contains a small patch that flushes almost denormal numbers to zero ... it helped to reduce cpu spikes on my p4 ...
cheers...