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  #1  
Old 02-13-2009
kimandsally kimandsally is offline
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Default Single or Multi 12v rail?

Hi there I've been around on here for some time and although I "should" know the answer to my question I would appreciate others opinions please.

I use my PC in a way quite differently from most people, I do game a little but would never go SLI or Crossfire but I do have a healthy thirst for overclocking.

My PC consists of 3 water systems with 3 pumps along with 6 hard drives and 10 120mm fans, then a Q6600 overclocked to 4.05 Ghz with 1.6v.

All this adds up to needing quite a powerfull PSU especially when I do my overclocking as I up the voltages even more to try to get every last drop.

So do multi rail PSU's work properly in this situation ie will they let some power go to the rails I'm using and not be wasted on a graphics card that is not fitted?

All this adds up to I'm thinking of getting a Enermax Revolution PSU.

Thank you for your time
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Old 02-13-2009
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http://www.jonnyguru.com/forums/showthread.php?t=3990

Which Revolution? If you're thinking about the 850W version, you might also consider Antec Signature or Seasonic M12D, but from what I've seen in reviews, the Revolution is also a very good PSU.
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Old 02-14-2009
kimandsally kimandsally is offline
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Originally Posted by Lemmy View Post
http://www.jonnyguru.com/forums/showthread.php?t=3990

Which Revolution? If you're thinking about the 850W version, you might also consider Antec Signature or Seasonic M12D, but from what I've seen in reviews, the Revolution is also a very good PSU.
Yes I considered those as well, but my main concern is because nearly all my amps will be used on everything except graphics cards will the PSU allow the AMPS to go where it is required.

I can see no point in a multi rail PSU for my needs if some AMPS is left to go down a wire with nothing at the end of it. Otherwise I'm paying for AMPS that I will never use, I will only ever have one GPU.

Hope this helps it's a strange request I know, I also know that I might struggle to use all the AMPS of a 850W PSU but I want something that will last because I looked at my reciepts and I have spent a silly amount of money on PSU upgrades in 4 years, I might as well buy one that will cope with anything then I won't need to buy another the next time a more power hungry CPU or something comes out.
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Old 02-15-2009
davidhammock200 davidhammock200 is offline
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Single Rail, that way your +12V amperage is available where ever it is needed.
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Old 02-15-2009
kimandsally kimandsally is offline
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Originally Posted by davidhammock200 View Post
Single Rail, that way your +12V amperage is available where ever it is needed.
I was fearing this, I was hoping against reality that if I wished enough that the Antec Signature or the Enermax Revolution would open the the way to let it go where required if it needed to.

My problem is I want everything Power Quietness efficientcy and Modular.

Looks like the Corsair 850 then what do you think david hammock?
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Old 02-15-2009
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Default It works just like your household circuit breaker panel.

See also Wikipedia on the subject.

Just like your house wiring, it's not safe to run more than 20A through a single ordinary wire. So when PSUs began to produce more than 20A, the ATX power supply spec added a requirement that, in addition to an overall overcurrent limit (the main breaker in your house), each wire had to have a 20A current limit. Just like your household box has individual circuit breakers in the 1520A range.

Now, a separate current limit circuit per yellow wire would be a ridiculous expense, so the wires are grouped into "rails", each of which has a limit. Obviously, if the total is below the limit, each individual wire is, too!

The problem is, PSU manufacturers cheaped out and used the smallest number of rails they could. So you had a 40A limit divided into 20A on each rail, when it would have been much more sensible to divide it into at least three rails.

This was an annoyance to customers, and PSU manufacturers had two choices: add more rails (costs money), or do away with the extra safety circuitry (saves money). Guess which one they picked? For a while, you saw some "rail fusion" features that would light up an LED when the per-rail overcurrent trips rather than turning off the PSU. That's called a quick retrofit.

For a multi-rail PSU, a good indicator if quality is the sum of the rails divided by the total +12V limit. Ideally, it should be 2 or more, but in practice you're doing well if you get 1.5.

Really, it's just a matter of not plugging all the heavy loads into the same rail, just as if you plug a floor polisher into the same kitchen circuit with the fridge and the microwave, you'll trip the breaker.

But a single-rail PSU is certainly simpler.
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Old 02-15-2009
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Quote:
Originally Posted by kimandsally View Post
So do multi rail PSU's work properly in this situation ie will they let some power go to the rails I'm using and not be wasted on a graphics card that is not fitted?
Read this yet?

http://www.jonnyguru.com//forums/showthread.php?t=3990

The OCP on the Enermax is set to 30A on all six 12V rails. You're not getting up that high with what you have planned to run on it.

Last edited by Oklahoma Wolf; 02-15-2009 at 08:02 AM.
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Old 02-15-2009
kimandsally kimandsally is offline
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Originally Posted by Oklahoma Wolf View Post
Read this yet?

http://www.jonnyguru.com//forums/showthread.php?t=3990

The OCP on the Enermax is set to 30A on all six 12V rails. You're not getting up that high with what you have planned to run on it.
I've read the sticky a few times sort of have the idea, it's this OCP that puts the spanner in the works for me, I look at the Enermax with 6 rails and I assume I will only be using 3 with 1 GPU?

I think the bit I cannot grasp is these PSU's often have enough cables for 4 GPU's and allthough I want a powerfull PSU I don't want something that will have power going down 3 rails that I could never use even if I needed it.

I'm assuming I will probably only draw just over 600 watts even when more powerfull stuff comes out, (currently my set up uses around 260watts idles from the socket going up to just over 440 watts is the most I've eve seen)

My theory is when in use my power input is around 320-370 watts so I'm looking for a PSU that has it's maximum efficientcy at that wattage.

Maybe it would be better to ask you what PSU would you buy? This time money is no object because I intend this one to be the last for 4-5 years so I need something that is future proof as possible.

Thanks for your input.
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Old 02-15-2009
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Quote:
Originally Posted by kimandsally View Post
I don't want something that will have power going down 3 rails that I could never use even if I needed it.
It won't have any power going down cables you're not using. Even if you only use three of the six 30A 12V rails on the Enermax, that's still 90A of combined capacity available to you. The unit is only rated for 87A combined. There's no problem. No "trapped power." You're overthinking this, methinks.
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Old 02-15-2009
kimandsally kimandsally is offline
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Quote:
Originally Posted by Oklahoma Wolf View Post
It won't have any power going down cables you're not using. Even if you only use three of the six 30A 12V rails on the Enermax, that's still 90A of combined capacity available to you. The unit is only rated for 87A combined. There's no problem. No "trapped power." You're overthinking this, methinks.
Sorted that's what I wanted to hear, although I've read every single review on here I just don't have the confidence to be sure, now it's come from you I feel totally happy buying a multi rail.

All I need now is before I consider spending my money on the Enermax is your review, if it passes your tests and you think it's as good or better than the Signature or the new Sea Sonic M12D, I'm looking forward to seeing how the 91% eff holds out and compares to the the Signature and the M12D.

Thank you for your time I do appreciate it.
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