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Thread: Which PSU?
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Old 29-04-19, 12:43 PM
tgrech tgrech is offline
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[TL;DR: A Titanium PSU will output almost half the heat of a Gold rated PSU(~6% of draw as heat vs 10%) most of the time and therefore should require less active cooling.]

Originally Posted by SuB View Post
Having more headroom (so having the 1000w) = the fans will stay off for more time (especially on an RM) and will run quieter and cooler overall,.

Having less watts (850w) = driving that harder = probably more noise...

It really is mostly that simple, you're correct.
Well, sort of, a higher rated PSU should be have better cooling to match, but the noise is a result of moving the waste heat energy, the waste heat energy is calculated from the efficiency. A titanium 850W PSU should be 4% more efficient in the main power band(40-60% load), with that rising to 5% just beyond that, and critically any PSU below a Titanium doesn't have an efficiency certified for idle or heavy loads, so that gap could widen further outside of 25-75% load. For a Gold rated PSU you typically see curves like this(Image from Corsair):

I know 4-6% efficiency might not sound like a lot, but if you're pulling 600W that's ~25W of heat (Titanium 230V peak eff.) vs ~50W(Gold 230V peak eff.), which very well could be the difference between fans spinning or not, and remembering peak efficiency is the best case scenario of comparison for the Gold PSU(Though ofc at lower wattages the absolute gap shrinks even if the %age eff. widens).

Using an overspec'd PSU also harms efficiency in itself(Though ofc so does using a heavily underspec'd one), if they're not in that 25%+ load gap most of the time(And it's very rare your PC would draw 250W+ unless under notable load), then their PSU won't be running to a rated efficiency at all with a Gold, while with the 850W Titanium it'd be in its rated efficiency range as low as 85W. Assuming they rarely go over 750W load (Which would take some serious overclocking with those parts, remembering this is not load at the wall we're worrying about which is typically 10-20% higher, those parts would probably have an internal draw of about 500W while gaming) the Titanium 850W should be roundly more efficient and therefore quieter assuming roughly equivalent fans & internal dissipation rate.
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