Quote from: tigerbit on July 24, 2013, 09:07:56 PM

Quote from: knedle on July 24, 2013, 08:28:20 PM

Quote from: pajak666 on July 24, 2013, 04:37:00 PM

where can I find a link or a list of PSU that don't require minimum load on 3.3V & 5V rails? google didn't helped:/

Try looking for a PSU that draws 3.3V and 5V from 12V rails, usually they will be marketed as 12V only PSU, DC-DC PSU, also a lot of PSU with single 12V rail will be in that group. Also all of those PSUs will be more expensive, that those requiring load on 3.3V and 5V, so you may consider buying cheaper PSU and powering with it a couple of fans, or an ethernet switch.

Quote from: SebastianJu on July 24, 2013, 05:15:45 PM

I never heard of this. You have to draw power from these lines?

All cheaper or older PSUs require that, if you do drain any power from those lines, 12V line may be unstable. Since all computers require some power from 3.3V and 5V, until few years ago it wasn't considered a problem. If you want to know more you can google for "one computer two PSUs", or something similar.

Check out your desired PSU (or whatever is available locally) here: http://www.jonnyguru.com/
This guy runs detailed load and regulation tests. The tests you're interested in are the Crossload tests (particularly CL2 the 12V one) where he creates a maximal load on 12V or 5V and checks voltage regulation and ripple. As has been pointed out, most top end high power PSUs don't actually require small loads, although the ATX specification says there should be one.

If you want to go cheap homebrew then you can always build this for <5 EUR.

Generates the min loads using power resistors on 3.3V & 5V to keeps a small stack of FPGAs running on a cheap 20EUR 460W PSU. Mk II should see me running the Raspberry Pi and USB HUB off the 5V line so I can remove the 22Ohm resistor on the 5V rail that does get a bit warm. Of course, my bitburners will be running off something like an Antec HCP 1200 that doesn't require the loads anyway - but it's two less plugs in the wall if I have the Pi and USB hub powered from the standby 5V, and I can even have an on off switch for the main load.

Biggest PSU isn't necessarily the best. Most expensive, maybe. Buy what you need - don't build in too much overhead on wattage. You're better off spending the money on a decent branded PSU. Personally I plan to load the 1200W Antec HCP or Corsair around 90-94% of max-rated 12V load. Check out the tests at jonnyguru and it'll show you how these PSUs perform at varying loads. Most often for a decent branded supply the efficiency at full load is pretty much within 1-2% of optimal - its when the PSU operates at lower loads the efficiency falls off a cliff. btw - my logic is based on running 12 XX & 1 X with as much overclock as I can reasonably handle on air (planned for 90W per board).

I plan with 100W per board since one board used 94W at 450MHz and 1.3V. So its a bit space for more wattage need. I originally wanted to use smaller psu's with 600W but realized, when 40 miners match into one 2U-Rack of 750mm depth and they use 4000W then i would need a lot psu's. So better safe some space by using bigger ones. The price is peanuts when compared to the costs of the miners so i think saving money there is saved at the wrong point.

I searched for tests and found that this model is said to have very stable power supply, it was marked on of the best. So i think its a good choice. Or do you have other info?