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Old 03-08-2009, 09:39 PM   #1 (permalink)
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Default Yet again PSU question

Originally, a power supply featuring "multiple +12V rails" implied one able to deliver more than 20 A of +12V power, and was seen as a good thing. However, people found the need to balance loads across many +12V rails inconvenient. This problem was exacerbated by the fact that the assignment of connectors to rails is done at manufacturing time, and it is not always possible to move a given load to a different rail.

Rather than add more current limit circuits, many manufacturers are ignoring the requirement and providing "single-rail" power supplies that omit the current limit circuitry. Although capable of starting a fire under the appropriate circumstances, there have not been a noticeable increase in accidental fires, and as of 2008[update], product safety testers like Underwriters Laboratories continue to approve the supplies.

For a time, power supplies were marked and sold as having multiple +12V rails, although no current limit circuitry was included. As of 2008, having only an overall +12V current limit is seen as a desirable feature, and "single-rail" power supplies are advertised and sold as such

This was on wikipedia. So I again come to this load balancing thing. I would have no idea what to do or what that is. Is this the case anymore, if I buy a PSU with 2 or 4 12v rails will I have to do any load balancing?? Sorry for the repeated question

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Old 03-08-2009, 10:17 PM   #2 (permalink)
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Default Re: Yet again PSU question

Wikipedia isn't a reliable source, I've been told that, numerous times by my professors in college. Anyone can write what they want on there. But no, load balancing wouldn't be necessary.


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Old 03-09-2009, 07:43 AM   #3 (permalink)
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Default Re: Yet again PSU question

Load balancing simply means you have to be aware of what hardware is being powered by each rail. For example if the psu had 8 x 18a 12v rails but you connected 3 gTX 285's and a Core i7 so they were all drawing power from one rail you would have some serious problems since 18a is no where close to enough for all that hardware.

The psu should have the connectors set up so that wouldn't happen (ex the cpu power cable running off one rail and the pci-e connectors distributed evenly among the rest of the rails) but if you are pushing the limits of the psu it's something you should still be aware of.

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Old 03-09-2009, 03:49 PM   #4 (permalink)
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Default Re: Yet again PSU question

easy solution, if your worried about it - buy a psu with a single 12v rail

Originally Posted by Puddle Jumper View Post
The psu's should have the connectors set up so that wouldn't happen

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