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Are PSU Load Calculators Accurate?

N

nbuubu

Limp Gawd
Joined
Dec 7, 2009
Messages
216
I ask because I have an old Corsair HX620W that's been good to me for a long time. It's seen about 3 years of heavy heavy use.

I recently upgraded to a GTX 580 and didn't have the correct power cords (was missing the 8pin GPU connector, so I used the adaptor with a pair of molex) and I've been experiencing a handful of odd crashes that make me think my PSU is overloaded.

I've plugged every single piece of kit I have into several web-based calculators, and they all say I need at least a 790W power supply. Always figured the calculators were just marketing tools that inflated numbers to make us buy more than we need.

But I've been having some rare reboots and some crashes in WoW that lead me to believe my ram and/or my 580 may be getting a little less power than they need.

Just pulled the trigger on a Corsair AX850 figuring I'd need some more overhead. Was that a bad move? Should I have spent some more time troubleshooting? Just thinking my crash symptoms are looking more and more like an aging/overloaded PSU.
 
Your issues sounds like it could have been caused by a defective PSU.

But in general PSU load calcs are not that accurate. Use them for ballpark readings at best. Maybe +/- 100W or so.
 
Indeed PSU calculators, depending on which one, will give you the full load spec and "worst case scenario".

However, purchasing a Corsair AX850 is not a bad idea, its a DAMN good PSU.
 
Thanks for the replies. It may not be a PSU problem, but the fact these calculators show me at 170W over my 620's max, means it could very well be.

Fingers crossed this stops the random restarts.
 
From whatI can tell most calculators give you about 100W of head room. You are undoubtedly underpowered by at least 70W. The new PSU was a good decision
 
I had similar problems, and upgraded to Corsair HX1000w (included a water cooling kit on top of a 6870 tune-up) and it resolved everything. Hope you have the same luck.
 
nbuubu said:
Just pulled the trigger on a Corsair AX850 figuring I'd need some more overhead. Was that a bad move?
Click to expand...

Not a bad move. Its kind of like insurance. Too much might cost more than you need to pay, but too little will really bite ya. That is an awesome PSU and I would love to stick one in a new build, so yeah, no problems there. But the old one, you still need to troubleshoot it and I think they have a 7 year warranty. Its still an awesome PSU if you get it fixed so see if its broken. If you are having problems when your system is NOT at full load, something is wrong with that PSU because its pretty hard to draw more than 52 amps on your 12v rail with one (single GPU) video card. That 790 watt draw calculation seems way too big. In fact EVGA suggest a minimum of a 600 watt PSU with 42 amps on the 12v rail for a single gtx 580 and you know they are being conservative. If that HX650 isn't doing the job, something is wrong with it.
 
Unknown if it's a psu issue or not, although the psu you got will be awesome. But I'm gonna say psu load calculators can by off by way more than 100w. I think sometimes they're off by 300w+. All depends which settings you use. Most of them massively overestimate every single component. I think testing my own computer's parts on some calculators, I was off by at least 150w from actual power usage.
 
If your spec are right you are pulling around 350-400watts under load. You have to remember that power supply degrade over time so it could have been your power supply. I wouldn't want to run a power supply at 70% of capacity. Plus it always fun to buy new stuff :)
 
It's always good to measure the power with a KILL-A-WATT meter or equivalent. I used a free online calculator recently and it size it the power supply pretty close. I picked one about 2X the recommendation. The power supply ended up about right at 40% load idle and 60% maxed out.
http://extreme.outervision.com/
 
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