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slowmo on 27 April 2010
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nordlead said:
Squilliam said:
nordlead said:

this is one of the dumber theories in the PC building world (right up there with needing 20 case fans to cool a rig). Power supplies should be at 80% load during max load for maximum efficiency. I got conned into a 600W supply once with one of my PCs which typically only draws like 120W idling because I didn't understand power supplies at the time. I should have had a ~350-400W supply.

So, if you have a PC that truly draws 400W under full load, then yea you need a 500W supply, else you are just losing efficiency especially when it's just idling. If you upgrade often, then just make the PSU part of your upgrade plan and sell the old one as they really don't drop in price (unlike other hardware components)

But, but the PC has to have an internatl temperature fewer than 5 degrees above ambiant under load!

Btw, shouldn't a 80+ PSU have sustained efficiency throughout the wattage range? Thats what the certification is about.

I've seen some studies that showed the best cooling accomplished was with 2 fans (plus the PSU fan). They used identical computers with varying fan setups. The theory why it outdid the other combinations was the over abundance of turblance caused by the manny fans slowed the overall cooling rate. All I know, is that so long as you have decent airflow over the hot components you should be good. Adding 5 more fans generally doesn't help. I can't find the test I found before, or I'd link you to it.

I just looked up the 80+ (which I understood wrong) and you get sustained 80% minimum efficiency from 20% to 100% load, but some PSU's get 85% or better in the 50-80% load range. Obviously your best bet would be to look at the efficiency chart for the PSU you are considering and map it to your estimated power requirements.

As longs as you have a clear pathway for air in and out of your case then the number of fans is of less importance.  I have 2 intakes at the front of my case which push air over the HDD's, I then have 2 exhaust near my graphics cards and one at the rear to pull the hot air coming off my CPU cooler out of the case.  My GPU, CPU and ambient temperatures are fine even with a reasonable overclock on my CPU. 

Where things go pear shaped is people installing fans not knowing the difference between a intake or exhaust and inevitably they end up with lost of fans pushing air into the case but nothing pulling out the hot air efficiently.  Ideally you want cool air being pulled in and that then pushes the hot air straight out.  I know my system vents heat out very well as the room temperature my PC is in goes up noticably with the PC running while the PC itself isn't even warm to touch (LianLi aluminium case, quite old now sadly).