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Four 12v rails or one high power 12v rail?

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April 26, 2010 5:55:31 PM

Hi all

i am looking Buy a new power supply for my rig i have narrowed it down to a choice of 2 but dont know which of the 2 would be better, or they both have pro's and con's. I have looked @ antecs CP series designed for my case but this has not got enough conectors for my rig

Antec 850W TruePower Quattro Modular PSU (four 12v rails )
or
XFX 850W Black Edition Single Rail PSU (one high power 12v rail)

The XFX is more efficent being 90% rather than the 80% on the antec, But saying that for 10% the Antec would inprove airflow in my case.
other than that i dont know which would be better as the tittle says "Four 12v rails or one high power 12v rail" which is better?


ps i dont need to know what size power supply to use thats not what im asking.
a c 164 ) Power supply
April 26, 2010 6:05:41 PM

that xfx model is actually a seasonic with a XFX label tossed on. Its a great PSU!

The Antec is also very good so you can't really go wrong with either one but I would go with a Seasonic PSU over an Antec one.

*yes I know Seasonic makes Antec's lower truepower units and earthwatt units :wahoo: 
April 26, 2010 6:15:07 PM

Get the XFX. Where the Antec is calling multiple rails a "feature", it really is a way to cut costs on the PSU. You're more likely to have to run extra cables in your case to keep everything balanced.
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a c 243 ) Power supply
April 26, 2010 7:36:02 PM

The XFX is the better power supply, the number of rails is pretty much meaningless.
April 26, 2010 8:15:51 PM

delluser1 said:
The XFX is the better power supply, the number of rails is pretty much meaningless.

You say the number of rails his meaningless but it must have some pros and cons. I would like to understand the diff bettween them before i commit to buy. Tho from whats been in this thread and the fact that the XFX psu is allready in my shoping cart then thats the one i will have :) 

But as i said i just want to understand the differance between them more than anything else. As antec claim four rails are better and XFX claim one high power rail is better im confused, and i think others will be confused by this aswell. :ouch: 

Hence i am looking for some of them clever ppl out there to tell us all the differance between four 12v rails and one high power 12v rail :hello: 

April 26, 2010 8:38:53 PM




Thats what i was looking for thankyou.

I now understand the differance and its the single rail for me ta. I would prefer to burn out than to fade away :D 
a b ) Power supply
April 26, 2010 11:45:42 PM

WHY SINGLE RAIL:
Single rail is practical to use these days of high current load from GPU, CPU, additional drives. It avoids a situation of shortage current of a specific rails (~ i.e. 18A rail) on a GPU. Not all users have the proper tools and knowledge to manage and distribute load properly on a multi-rail system.

Single rails you have all the capacity in one current source. Single NODE source. It eliminates the mistakes/errors of overloaded rails.

WHY MULTI RAIL.
1)The multi rail supply was partly a result of the desire to separate the electrical LOOP of critical and non-critical load. CPU, GPU can be separated from the motor base load such as Hard Drives , Optical disk , and fans. The advantage of this multi-loop setup is the electrical noise from non-critical loads are isolated from the critical load.

Well this need is not an issue today. The boards and electronics are well design for all the motor and electronic loads to be on the same loop. One source of 12V rail.

Unless you have a super sensitive board (i.e. high end audio processing board for editing / recording) you don't need an isolated 12V rail.

2) The technology now is available to make switcher supplies with extremely high current and better PWM control. Before to make high current the practice is to GANG current drivers to produce a high current source. Now MOSFET, TRIACS, & ISOLATED GATE Transistor can handle large current that wasnt available today.

If you are good in electrical load calculation and management. You have a need for low noise environment that you need to isolate certain load on your PC the Multi-rail is better.

-------------------------------

I hope i made it simple enough for common readers(No Electrical Engineering Required)

Not all PSU are made the same. A good reference is the site below

http://www.jonnyguru.com/index.php


I recommend a single rail supply than the multi rail psu. Corsair PSU is my preferred these days... XFX is one the best base on the latest review.

Its your choice you know what you need
a b ) Power supply
April 26, 2010 11:48:00 PM

correction:

Now MOSFET, TRIACS, & ISOLATED GATE Transistor can handle large current that wasnt available before.
April 26, 2010 11:51:46 PM

Yes leon prerty much what the link delluser posted says(tho this goes into more detail) im glad someone took the time to write it out a simpler version here for toms users to see
a c 144 ) Power supply
April 27, 2010 5:59:23 PM

I also favor single rail PSU's

cmcghee358 said:

Makes me hate my cheapo PSU a little bit more tho...

And so you should. :) 
April 27, 2010 6:11:51 PM

cmcghee358 said:
Now THAT was enlightening!

Makes me hate my cheapo PSU a little bit more tho...



Hell yes i feel a little more clever now i read that LOL

April 28, 2010 2:19:34 AM

ok a wee question to do withthe XFX blsck psu. That horrid green fan is it possible and safe to change it for one a little easyer on the eye?
a c 243 ) Power supply
April 28, 2010 2:28:41 AM

How often are you going to see it ?
Opening your psu will void it's warranty.
April 28, 2010 2:31:16 AM

delluser1 said:
How often are you going to see it ?
Opening your psu will void it's warranty.


I have a Antec 1200 case so every day lol.
Either way i would open it up every now and again to clean out the dust as i do with my other psu's
a c 243 ) Power supply
April 28, 2010 2:51:31 AM

So you void the warranty on all of your power supplies ? Wouldn't it be simpler to just use a can of dust off or a compressor ?

Switch your case over to a green theme, a couple of green Tricools and a green cold cathode in the top would make the XFX less of an eyesore.
a b ) Power supply
April 28, 2010 2:54:31 AM

Or even blue cold cathodes work well to play off the green themed PSU.
April 28, 2010 2:58:15 AM

delluser1 said:
So you void the warranty on all of your power supplies ? Wouldn't it be simpler to just use a can of dust off or a compressor ?

Switch your case over to a green theme, a couple of green Tricools and a green cold cathode in the top would make the XFX less of an eyesore.


I get your point but have no choice one of our children has an allergie (ive never been able to spell that word but im sure you get my drift) to dust mites so i have to vacum not blast. Also it dont matter with the psu's i have atm as they are either vvvvvvv old (in the Dell) of are Jantec psu's who no longer exist.

PS leaveing the dust there is not an option either
a b ) Power supply
April 28, 2010 7:49:32 AM

Eithelwulf said:
You say the number of rails his meaningless but it must have some pros and cons...................................................................................................................
Hence i am looking for some of them clever ppl out there to tell us all the differance between four 12v rails and one high power 12v rail :hello: 


Well since you asked.

Back before the ATX 2.0 spec about 5 years ago, just about every power supply was a single 12v rail. A big one could have 40 to 50 amps back then.

Then Intel (the author of the ATX spec) decided it didn't want more than 18 amps being drawn off any given 12 volt rail and came out with ATX 2.0. It called for 12v rails being no more than 18 amps and shuting the unit down at 22amps. Leon2006 gave a pretty darn good account of the reasoning in his post.

So the initial round of multi-12-v-rail PSU's came out and it cause lots of problems. It was fairly easy on a high end system to hit 20+ amps on a rail which, if the PSU followed the ATX 2.0, would shut it down. Didn't matter that there was plenty of power on the OTHER rail. They couldn't share. Before ATX 2.0, they were on one big rail they all shared.

Now nobody HAD to follow the spec. PSU's continued to worked just fine the old way, but everybody wanted to be able to say "We are ATX 2.0 compliant".

It became such a problem that gradually company's started ignoring the spec. PC power & cooling just ignored it outright. Enermax moved the cap up to the mid 20's and claimed it was ATX 2.0 compliant even though it wasn't. Corsair and Seasonic didn't even have multiple rails but just claimed they did.

Eventually, Intel realized they screwed up badly and changed the spec.

Today, most PSU's have gone back to single rail, but even the multi-rail designs have plenty of headroom on each rail now. So there is really no practical difference to the end user.
May 3, 2010 9:06:06 PM

Hope i dont seem dumb asking this question but i cant seem to see how to select the best answer to any of my threads?
a b ) Power supply
May 5, 2010 12:46:26 AM

Dellusers link is the most enlightening imo.
a b ) Power supply
May 6, 2010 3:41:35 AM

Eithelwulf said:
Hope i dont seem dumb asking this question but i cant seem to see how to select the best answer to any of my threads?


The bottom line is, both units are great units. You will be happy either way. They are both great, and the rail difference is negligable in todays PSU's. Build quality is the most important element and both these bad boys have it.

------------------------------------------------------------------------------------------
For those interested in a more technical answer, likely nobody, but here we go..........

A lot of the confustion on this topic was caused by intel. Prior to their changing the ATX spec in version 2.0 to limit any 12v rail to 18 amps, just about every PSU was single rail and nobody thought anything of it.

Problem was, most of those initial batches of multirail PSU's had only two rails, each capped at 18amps. So even a big PSU had 18amp for the cpu and 18amps for your GPU. Thats 18amps for ALL of your GPU's. If they topped 20 amps of draw, the OCP would shut the PSU down. And this was surprisingly easy with a high end card. Especially with SLI or Crossfire. And several units had less than 18. 14 and 15 amp rails were common.

Think of it this way. You have a cpu that draws 10 amps and a SLI setup that draws 22 amps under full load. On a single rail with 35 amps shared between the cpu and the GPU's, thats 32 amp total draw. No problem for a 35 amp unit.

After ATX 2.0, the same unit from the same manufacturer, would have the 12v rail split into two 18amp rails. Now the cpu is still fine at 10 amps with 8 to spare. But the GPU's are going to trigger the OCP because unlike a single rail where all the amps are shared they cannot use the 8 amps that the cpu isn't using because its isolated on the cpu's rail. The 22 amps it draws is too much for its rail and the PSU shuts the system down. This happened to a lot of gamers and is why multirail PSU's got a bad name.

Eventually, Intel dropped the requirement. Also, you started to see a unique rail for each GPU instead of just one. Manufacturers who stuck with multirail units have raised the caps well above 18 amps so multirails really stopped being a problem, but the reputation persists to this day.

If your really hardcore, you probably want a big single rail since a super duper overclocker with quad SLI might still trigger OCP even with the higher rails. But hardly anyboady falls into this category.

On the other hand, there is a slightly higher risk that a single rail will have a malfunction which will take your hardware with it. This is because some motherboard shorts will not trigger the PSU short circuit protection and the big rail will damage hardware even if there is OCP. This is only really a problem on the really big single rails, like 70 amp + and is very rare, but worth noting.
May 7, 2010 11:37:38 PM

I'll throw my hat into the history ring and tell you that the reasoning behind Intels 240VA limits was due to a certain commonly used transistor that would catch on fire at around 35A and instead of simply calling for a sub 35A limit some engineer said "hey there's already a 240VA safety regulation in place for user accessible circuits and we can just cite that". Problem was that 240VA wasn't enough for future GPU demands but you see the Intel ATX spec was defined for use in conjunction with the Intel CPU voltage regulator guide and didn't take into account GPU demands...and still doesn't. The PCIe connector, which was originally an Nvidia invention isn't even defined in the ATX spec and only the EPS spec for servers and workstation graphics accounts for this connector.

Really problems with the 240VA limit have only arisen on dual rail units, multi-rail units that for some dumb reason used limits even lower than 20A on some rails (which is the mistake PCP&C made with their four rail Turbo-Cool 1000 and decided to do away with multirails altogether) and certain multi-rail units that put too many connectors on one rail. A modern multi-rail unit isn't likely to have this problem but it doesn't mean that engineers are infallible.

You can see the OCP trip points for the Antec Quatro 850 here:

http://www.antec.com/Believe_it/product.php?id=NTg=

36A on all four rails...this isn't going to be a problem in the foreseeable future.
a b ) Power supply
May 8, 2010 4:25:47 AM

Thank for the info Makalu. I always wondered where that seemingly arbitrary 18 amp/240VA limit came from. I knew about it, but never knew why.

Today most enthusiast multirails are like the antec quatro you mentioned. The all have plenty of juice. But reputations die hard sometimes.



a b ) Power supply
May 8, 2010 2:11:33 PM

ok, so i bought a coolmax cu-500b. why is it triple rail for such a cheap psu?
a c 243 ) Power supply
May 8, 2010 2:13:26 PM

shovenose said:
ok, so i bought a coolmax cu-500b.

Don't know that I'd advertise that fact.
May 8, 2010 2:21:15 PM

Eithelwulf said:
Hope i dont seem dumb asking this question but i cant seem to see how to select the best answer to any of my threads?


Ok i think you missunderstood what i was asking.

For for instance lets say i want to sellect Dellusers link as the best answer in this thread, As it was a quite quick reply gave me all the info i need and others seem to have found it interesting.

I dont seem to be able to select best answer in my threads as i see others doing. (its probably stareing me in the face)
a b ) Power supply
May 8, 2010 2:26:44 PM

its a button in the corner of his post
bottom right cornewr, marked select as bes t answer
May 8, 2010 2:46:28 PM

all i can see there is reply to post button humm
a b ) Power supply
May 8, 2010 2:54:30 PM

are u logged in?
May 8, 2010 3:04:00 PM

yup or i wouldnt be able to post lol :p 
All i can see in bottom right of posts is add to quoted button and reply to personbutton
a b ) Power supply
May 8, 2010 3:05:44 PM

good point, are u sure its not there?
a b ) Power supply
May 8, 2010 3:06:50 PM

o nevermind thats a stupid question.
new and improved question: what web browner? cuz though the 64-bit version of ie is lots better than the normal version, occasinaly it has trouble doing certain buttons and media.
May 8, 2010 3:18:42 PM

cuold be the issue im useing the 32 bit browser the 64 bit crashes to offten, tryed fire fox before similar results. Im ordering win7 with my psu, i hate this OS its so buggy but not had the cash to replace it.
May 8, 2010 4:06:40 PM

^You can't select a best answer because you started a "discussion" thread instead of a "question" thread.
May 8, 2010 4:09:17 PM

logan the huge said:
^You can't select a best answer because you started a "discussion" thread instead of a "question" thread.

ah ok feels real daft now lol
!