Processors in most early x86-based computers, up to some of the early 486s, did not need active ventilation. Power supplies needed forced cooling, and power supply fans also circulated cooling air through the rest of the PC with the ATX standard. The byproduct of increased heat generation is that the fan(s) need to move increasing amounts of air and thus need to be more powerful. Since they must move more air through the same area of space, fans will become more noisy.