I want to upgrade from a Radeon HD 5450 to something that doesn't force me to play Skyrim at 800x600 just to get a playable framerate. My PSU is marked as 365 watts — not too bad on its own, but the other numbers are the reason I got the 5450 in the first place a few years ago:
Max combined power of 5.08V & 3.33V is 160W.
Gimme something. Should I risk money on an HD 7750?
(I can't upgrade the PSU because the system is a PoS HP Compaq)
There is no one answer. It varies from one power supply to the next.
Single rail,Dual rail,multiple rail.
But all have a set limit on the 12v rail(s).
On a single rail it is governed by the wire guage used and over current protction.
On Dual rails it could be 18amp per rail maximum, but a total of 30amp maximum. Meaning if one is pulling 18amp the other can only have 12 amps.
Multiple rails could be one single rail with over current protection on each rail. Or it could be 3 or 4 individual rails.