Single or Multiple +12v switch on PSU. What is it?

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Saro13

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Looking to build a new PC soon. I like Corsair PSUs so going with that. Specifically looking at the HX 750. Something that caught my eye was a switch on the left that says Single or Multiple 12v. Here's a pic below

biqpw3.jpg


Can anyone explain to me what that means exactly?
 
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Leave it on single. It makes no real difference these days since internally its still Single. It marketing to make you feell safer with multiple rail mode.

Single means all the AMPs can be applied to the a single 12v. where as multiple limits what each 6/8 Pin cable total amps are. Stops you from drawing say 50 Amps at once instead of 12-15 for each cable. It really just for a piece of mind, but internally its still a single rail system.
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ko888

ko888

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This is Corsair's explanation:

Toggle single +12V rail or multi +12V rail mode. In the “SINGLE” position, the full output capability of the power supply’s +12V rail is available to any and all connectors, while in the “MULTIPLE” position, each individual connector has Over-Current Protection so no more than 40A of current can be delivered on any given cable.
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iamacow

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Leave it on single. It makes no real difference these days since internally its still Single. It marketing to make you feell safer with multiple rail mode.

Single means all the AMPs can be applied to the a single 12v. where as multiple limits what each 6/8 Pin cable total amps are. Stops you from drawing say 50 Amps at once instead of 12-15 for each cable. It really just for a piece of mind, but internally its still a single rail system.
 
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turkey3_scratch

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It's not for peace of mind, it's so a shortage that is not detected by SCP but rather is seen as a load increase doesn't result in melted wires at the bottom of your case.
 
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iamacow

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Unless you are a serious overclocker with LN2, you won't short anything. Mutli and Single was a real thing in the past because internally the PSU was designed differently. Now they are all the same and a little chip is what controls this function. If you are going to short things, its still gonna melt either way.
 
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turkey3_scratch

turkey3_scratch

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Shorts have nothing to do with overclocking. It happens when there is a failure of some type. There used to be an article on a website showing single rail PSUs with melted wires or damaged connector pins, that's more common). Multi-rail is safer and costs more money because it is safer.

It's got nothing to do with the internal design, it's adding protections that check the output currents.

Edit: I misread what you said about melting. In a multi-rail unit wires/connectors are less likely to melt because the unit will shut off at a lower current.
 
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turkey3_scratch

turkey3_scratch

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Nope, multirail units have different protection ICs capable of handling multiple rails. If you take two units that are 100% identical except one is multi-rail and one is single rail, the multi rail will cost more to manufacture. This is a fact, not a guess.

Here are words from the mouth of Jonnyguru: http://www.jonnyguru.com/forums/showthread.php?t=3990

Safety. It's done for the same reason that there's more than one circuit breaker in your house's distribution panel. The goal is to limit the current through each wire to what that wire can carry without getting dangerously hot.

Short circuit protection only works if there's minimal to no resistance in the short (like two wires touching or a hot lead touching a ground like the chassis wall, etc.) If the short occurs on a PCB, in a motor, etc. the resistance in this circuit will typically NOT trip short circuit protection. What does happen is the short essentially creates a load. Without an OCP the load just increases and increases until the wire heats up and the insulation melts off and there's a molten pile of flaming plastic at the bottom of the chassis. This is why rails are split up and "capped off" in most power supplies; there is a safety concern.
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