Why factoring is single-core designed?

[sdbardwick]

Originally Posted by Vato

This is correct, and is true on most* OS and most* hardware.

The reason is that it makes for more even heat generation/dissipation within the CPU => cooler => more reliable => longer lifetime.

* most = all, in my personal experience, unless affinity has be used to override this.

I'll need some evidence that this behavior is by design. It might well be, but I am skeptical because that behavior could have a substantial negative impact on performance due to increased cache misses and loss of locality in cached data (i.e. Core 2 Quads sharing L2 cache over FSB).