Originally Posted by Iscaria
In all my years building computers I've always made sure to stay within safe levels on the power supply and have never really tried going over spec on a power cable. I currently have the Corsair TX650
which isn't cheap, but is about four years old. If the fix caps power from the PCI-E slot at 75W then about how much extra could I safely pull from the PCI-E cable? I think with overclocking it might go up to about 105W
You can pull 150w easy from a single 6 pin without any issues, probably much more but most tend to say 150w is safe for 24/7 draw through the cable.
18 gauge wire can easily handle 14 amps as a conservative rating, 16 when used in chassis wiring lengths. That is the actual conservative spec limits of the wire itself. So each wire can safely have 14 amps through it. Now, the PCI-E connector itself is rated by Molex (who makes the connectors) for 9 amps per pin, see here: http://www.molex.com/webdocs/datasheets/pdf/en-us/0455590002_CRIMP_HOUSINGS.pdf
That means that a 6-pin PCI-E connector conforming to spec and using only two +12v connections, can have 18 amps of power at 12 volts through it, which means safe rating by the people who make the stuff is 198-216 watts for a 6 pin. This is because to get wattage we multiply amps times voltage. So: 9 amps * 2 pins = 18 amps * 12 volts = 216 watts. if we account for up to a maximum of 1 volt of droop (which is excessive) then we would use 11v for the calculation, which gives us 198 watts of power.
For an 8 pin connector we have three +12v lines, which means: 264-324 watts.
if you look at one of my previous posts I also explained how the VRM section for the 3 phases tied to the PCI-E 6-pin power cable will handle the max safe wattage a 6 pin can deliver perfectly fine.Edited by EniGma1987 - 7/7/16 at 8:30am