[DiabloD3]

Not quite the answer you're looking for, but:

Some systems control fans via voltage (the old way of doing it), instead of modern PWM (which has been the standard for about a decade); and even with PWM, it should be viewed as an average of the voltage instead of merely as the peak voltage during pulses.

No matter how you end up controlling your fans, you're not giving them straight unfettered 12v, either you're controlling them via voltage (and they spend most of their time at around 5-7v), or you're controlling them via PWM (with a significantly reduced load cycle).

Some ultralight laptops have switched to 5v for their fans, but that does not seem to be any sort of standard. I have not seen a GPU that uses 5v for fans, and by the time GPUs needed big enough fans to have to control the speed on, they were exclusively PWM, and I am not aware of a GPU that used voltage control on it's fan.