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Topic: PSU partially died? Power supply requirements for two cards. (Read 316 times)

sr. member
Activity: 1246
Merit: 274
Well, it sounds most likely that your PSU is on it's way out at this point. If you have had it for several years, especially if mining during that time it's normal for it to eventually die from component degradation that all PSUs will have. Even good ones don't last forever. If you were pushing it's limits with mining then that will shorten the lifespan as well. If you at one point had 3 GPUs of 150 watts (Rx 480 stock tdp) that's 450 watts, a 130 watt CPU (more if overclocked) is 580 watts, a couple hard drives, RAM, and a few case fans can easily add another 50 watts for ~630 watts... if any of the GPUs or CPU were overclocked without being undervolted or having a tdp limit it's possible to have shortened the lifespan with a power load too close to it's max... esp if it's not a gold or platinum rated unit.

In any case, if you have already used it at least a few years I'd say you got your $ out of it at least. Smiley
newbie
Activity: 13
Merit: 0
I am mining with an RX 470 4GB and RX 480 8GB.  I have a watercooled intel core i7 920 socket 1366 cpu, hard drive, 2 DIMMS, and a handful of fans in the case.  I was using a Corsair Pro HX750W 750 watt supply, and it was working fine for a week with these cards, but today it shut down and would not boot or booted and then shut off when the GPUs kicked on.  I tried with the RX 470 alone and the RX 480 alone with the same results.  They would both boot up, but as soon as mining started, the power went off.

Is it possible that a GPU can just go from 750W to being only able to support less than half of that effectively ~350W?  Or is it more likely another component in the system developed a weak short?  I don't understand how it was working fine with both cards, but now it cannot support either GPU by itself.  This supply was supporting 3 cards of similar wattage a few years ago, and I never saw any issues with it.  One difference now is that I am not using riser cards, and the bottom card (RX 470) was directly above the PSU fan, so they were blowing their hot air at each other.

Assuming I need a new PSU, how should I choose the wattage if I am only using these two GPUs?  I tried putting my numbers in a few calculators, and they indicated I should be fine with 650W or less, but I want to be conservative since these are going to be running 100% 24 hours a day.  I know the CPU should not be consuming full power, so that should help offset GPU spikes.  But how much margin do I really need here?   If I killed this supply, I don't want to repeat that. 
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