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Old October 9, 2007, 11:46 AM
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Default Power Supply Myths Exposed!

I kept hearing and reading contradictory information about the amount of rails in PSU some people saying more rails are better while other people saying single rails are the best so I did a little research on my own about power supplies and stumbled across a good website Power Supply Myths Exposed! it is a good site and sure cleared up allot of confusion at least it did for me.
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Old October 9, 2007, 02:17 PM
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They make a couple of very good points, and aside from the bit about the fan size there's nothing in there that's even close to controversial.

That said, as much as I like PC Power & Cooling PSUs, as a general rule of thumb, a manufacturer's website is not the best place to find "unbiased" information..... :)
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Old October 9, 2007, 02:35 PM
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I agree with wilson even though there was nothing controversial it is not a good source to get an unbiased opinion. Our own SKYMTL is a good resource about power supplies as well as JonnyGuru.com
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Old October 10, 2007, 06:32 AM
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While I like what PC Power has to say in some regards, alot of their points are made to sell their power supplies instead of making any good technical points about the dos and don'ts of PSUs.

Many people don't remember this but less than a year ago that exact page contained points about why multi-rail units were better. This was due to their 1KW model being originally multi railed. Now that all of their units are single rail, they naturally had to change that.
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Old October 10, 2007, 09:56 AM
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Quote:
Originally Posted by SKYMTL View Post
While I like what PC Power has to say in some regards, alot of their points are made to sell their power supplies instead of making any good technical points about the dos and don'ts of PSUs.

Many people don't remember this but less than a year ago that exact page contained points about why multi-rail units were better. This was due to their 1KW model being originally multi railed. Now that all of their units are single rail, they naturally had to change that.
Interesting how they can condradict themselves. That's why I like getting an unbiased opinion from you or going to JonnyGuru.
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Old October 17, 2007, 12:12 PM
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All else being equal, I'd take a single rail. It's just one less thing to think about when you're plugging everything in. Every now and then, you stumble across someone who's having a computer problem, and the problem turns out to be too much power being pulled on one of the PSU's rails.
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Old October 17, 2007, 02:02 PM
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The point of having more than one rail for the +12v is thus:
Manufacturers did the dual,triple etc rail because having lots of amps (like say more than 34a with 70% efficiency could blow up the transistors), so they made the dual rails to balance the load on the transistors.
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Old October 17, 2007, 02:39 PM
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That only applies if the components are under-speced, though. When you have companies like PC Power and Cooling and Silverstone, that are both offering single-rail power supplies that put out 80 or 90 amps on the 12V, and do so in a safe and reliable fashion... clearly, there are ways of handling that level of power without resorting to completely splitting it up.

For that matter, there are some power supplies out there with 'multiple rails', that upon closer inspection, have been shown to be just creative wiring so they can claim compliance with the ATX12V Ver.2.2 specs.
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Old November 19, 2007, 10:30 AM
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Quote:
Originally Posted by SKYMTL View Post
While I like what PC Power has to say in some regards, alot of their points are made to sell their power supplies instead of making any good technical points about the dos and don'ts of PSUs.

Many people don't remember this but less than a year ago that exact page contained points about why multi-rail units were better. This was due to their 1KW model being originally multi railed. Now that all of their units are single rail, they naturally had to change that.
Exactly.

The SilverStone Strider was one of the first PSU's to take a 600W PSU and spread the +12V across four rails. Unfortunately, they messed up and grouped all of the PCI-e connectors on the same rail! This was because they were folllowing the SSI specification for SERVER power supplies that have multiple CPU's and large arrays of hard drives. Servers don't use high end graphics cards or SLI! This arrangement caused the PSU to shut down under high loads and because this PSU was SO POPULAR (at the time, all of the top scores on 3DM06 were people with Strider 600W PSU's) the problem became a pandemic and it gave split up +12V rails a bad rap. About six months later, SilverStone figured it out and had Enhance move the connectors around so the PCI-e connectors were split up across two +12V rails.

Shortly there after, PCP&C made the same mistake with their 850W. It was shortly after that they decided to make the 850W a single +12V rail and changed their marketing.

Fortunately, these days, PSU's with multiple +12V rails not only have their connectors distributed across the rails more appropriately for gaming machines than they were in the past, but also more power available per +12V rail. Even when they say the PSU "only" puts out 20A on any given rail, you could actually load the rail up to a good 22 or 24A before the PSU trips. You could easily run two high end PCI-e cards off of that.
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Old November 19, 2007, 10:35 AM
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Quote:
Originally Posted by Theblackmages View Post
The point of having more than one rail for the +12v is thus:
Manufacturers did the dual,triple etc rail because having lots of amps (like say more than 34a with 70% efficiency could blow up the transistors), so they made the dual rails to balance the load on the transistors.
Do you mean Transformers?
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