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View Full Version : your opinion: system power requirement and PSU leeway

fullmetal chocobo
11-05-2006, 07:56 AM
Background:
Back when I was first started running my dual Xeon machine, I had so many issues with power supplies and supplying stable power to the components, that I eventually went with dual PSUs, and getting an UPS, and that pretty much made my life a lot easier. Nothing worse in this world than losing two drives in a RAID 5 config, and losing everything. :( Still makes me sad...

Anyway, as a direct result to those times, I am very inclined to go overboard on the PSU for any rig that I build now, just so that the power available to the system is something that I don't have to worry about. And the only disadvantages to doing this are the extra cost of the PSU, and the possibility of running the PSU at a lower efficency due to operating at lower than full load.

My Question:
How do you select the power rating of a PSU for the build that you are doing? How much overage or leeway do you allow for? I would pull of some specific numbers, but I am at work, and I don't have any of the sites bookmarked that are good for "what size PSU should I get" kind of stuff.

Part of this has to do with the machine I'm planning for building, and part of it is out of geniune curiosity as to how others configure their systems compared to how I do.

Ya'll have a good one...
jonnyGURU
11-05-2006, 08:20 AM
These days, I look mainly at the 12V rail. So, like in your case, I might give 8A for each Xeon. And if I had a 6800GT in there, another 8 for the GPU. If there's more than two drives, I might start addinig 2A for each addiional drive.

Other than that, I look for good efficiency, minimal ripple and overall good build quality.
fullmetal chocobo
11-05-2006, 08:47 AM
These days, I look mainly at the 12V rail. So, like in your case, I might give 8A for each Xeon. And if I had a 6800GT in there, another 8 for the GPU. If there's more than two drives, I might start addinig 2A for each addiional drive.

Other than that, I look for good efficiency, minimal ripple and overall good build quality.

Interesting. Doing it that way makes it easy to see how I killed a few Enermax PSUs. :o Two Xeons, the vid card, 9 hds, and then the case fans (8x92, 4x120)...

*starts searching out 12V loads for all future components*
Veno(V)
12-05-2006, 07:53 PM
FullMetal Chocobo,

Did u ever decide on what to get? I skimmed thru your posts and never found out what you ordered.


Veno(V)
ParticularistEleven
12-06-2006, 03:52 AM
Jonny, that sounds like a great rule of thumb to go by. How do you know how much each component will draw from the individual rails? Is this knowledge gained by experience only? or is there somewhere were I can look up this stuff?
burebista
12-06-2006, 04:23 AM
For GPU here (http://www.xbitlabs.com/articles/video/display/power-noise.html) (you can look around for other GPU's).
For CPU here (http://users.erols.com/chare/elec.htm). Look after TDP (Thermal Design Power) and divide by 12 to get A (and consider ~80% Vcore circuitry efficiency).
For HDD here (http://www.silentpcreview.com/article657-page3.html).
For optical units you can roughly approximate like a HDD.
For a comparision between some MB's something like this (http://www.silentpcreview.com/article605-page4.html).
A nice article (http://www.silentpcreview.com/article313-page1.html) worth reading IMO, and a bit older but good to know: Power distribution within Six PC's. (http://www.silentpcreview.com/article265-page1.html)