I'm sure the answer lies somewhere in SMIT.

But that's a stock answer.

I'm not an AIX expert, but it seems to me that the way Unix timesharing works is that even if you have a single-threaded CPU-intensive process, it doesn't get parked on a single CPU, but will use whatever CPU becomes available. That means that it'll still use one-nth of the total CPU power in the machine, though, where "n" is the number of CPUs in the box.

If you're seeing particular CPUs overutilized, either AIX works very differently from other Unices (which is, of course, true in so many other cases) or there's something odd going on.

You might check out the "bindprocessor" command. It might lead you somewhere.