you can bet! its much more than valid.
The statement that heat alone can have a direct influence on speed? Are you sure?
From what I've seen, I'd highly disagree.
Heat certainly affects stability and lifespan of the chip/device. But I've not seen a direct correlation to speed, with the noteworthy exception of some modern processors which throttle speed back when a certain thermal threshold value has been exceeded. As far as I know, the PPC chips used back then had no such technology, and therefore shouldn't gain or lose a significant amount of raw speed based upon temperature.
Now, of course, what might have been meant is that if the device was running too hot, it might have had some smaller glitches and problems occurring, which were adversely affecting the apparent performance.
