I'm building up a spec for a new gaming rig, trying to get the most bang for the buck and gaming power.
So far I have the motherboard, CPU, RAM and an SLI configuration that I am happy with, and with some basic calculation have gathered that I need roughly 300w for the SLI configuration, and to play it safe 300w for the processor. Unless I'm being over estimate, I'd say a 700 or preferably 750w PSU is required.
However I am unsure which brands are the highest quality, and will provide for the system spec I am about to show you:
^ Umm... wow.... fail post and a fail product too. The Ultra X4 1200W only got a 5 for performance and 6.5 over all: http://www.jonnyguru.com/modules.php?name=NDReviews&op=... On the other hand, quality PSUs range in the 8.5+ for performance and 8+ for overall. Other top of the line PSUs (ie XFX 750 Black)get 9.5+ for performance and 9+ for overall. Next time, please don't post cr@p info.
The ATX12V specification includes a requirement for an over current protection (OCP) circuit in order to shut down any rail that pulls more than 240 W. In spite of this requeriment, several power supplies simply don’t carry this protection or only install it on the +5 V and +3.3 V rails but not on the +12 V, which doesn’t make any sense. There is a safety concern. Without an OCP on the +12V rails the load just increases and increases until the wire heats up and the insulation melts off, as you can see in this video that Antec has post in their Website:
Others manufacturers split up the +12 V output into groups of wires, having each group its own OCP. These groups of wires are called rails.
The PSUs that has been made with only one OCP circuit (or even no OCP at all) are called single rail. There is less components and less engineering to make a PSU that doesn't have the +12V rail split up, so it's cheaper to manufacturer.
The mutiple rail PSUs implies a better safety. The target of splitting up the rails is to limit the current through each wire to what that wire can carry without getting dangerously hot.
If you experience a short circuit in your system, OCP will cause the power supply to shut off, preventing excessive levels of current from flowing into your system and damaging the hardware attached to it.
Here you have a couple of videos about what happens when you short circuit a PSU with and without OCP:
Some brands like Enermax or Antec sell multi-rail power supplies which are engineered so that there is no way that you can possibly overload a +12V rail because each rail is limited by OCP (the OCP trigger point is configured by the power supply manufacturer).
All that said, in my opinion, the high quality single rail PSUs (like the XFX Black Edition 750W) are safe. However, the mutiple rail PSUs have a better safety.
The XFX Black Edition 750W has been made by Seasonic which is one of the best and older PSU manufacturer which have a great reputation for quality in all their products. This PSU is in fact a relabeled Seasonic M12D 750W (although the XFX PSU has a single-rail design while the Seasonic M12D has two +12 V virtual rails).
It supports even two very high-end video cards that require two power connectors each due to the four (6+2)-pin PCIe connectors.
All capacitors on this unit, both polymers and electrolytics, are Japoneses. In the primary this PSU uses two electrolytic capacitors from Chemi-Con (780 µF x 400 V in total) that are labeled at 105º C. Electrolytic capacitors from the secondary are also from Chemi-Con and labeled at 105º C. Very high quality.
It has a very high efficiency (80 Plus Silver certification) and very good voltage stability (voltages very close to their nominal values) and excellent ripple and noise supression on its outputs.
You even could reach 930W at below 50ºC.
The fan is a good 135mm ADDA ADN512HB-A91 fan which runs quiet and is audible at 70% load and up.
This power supply presents OPP (over power protection), over voltage protection (OVP) and under voltage protection (UVP).
All this with a 5 years warranty.
Seasonic has made a great job. I highly recommend it.