03-14-07
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#6 (permalink)
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SLI & CF PSU's
Updated 3-16-07
SLI & CF PSU's
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Originally Posted by webstien
I had to make this
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Quote:
As you will see all PSU's recommended for highend systems are Single +12V Rail PSU's.
This has now become necessary for several reasons:
PSU manufactures are now assigning the rails on their multi-rail (3 or more +12V rails) PSU's in whatever fashion pleases them.
Motherboard manufacturers are now requiring additional power connectors, beyond the standard ATX & P4/EPS connectors.
Sometimes the interaction of these unique rail assignments & additional power connectors results in mobo/PSU incompatibility.
All of these problems are of course caused by the ever higher power demands of ever more powerful GPU's.
Most Dual +12V Rail PSU's are not effected as one rail "should always" be used exclusively to power the CPU via the P4/EPS connector, however Dual Rail PSU's that follow the specs can not power highend SLI systems.
Therefore all PSU's recommended for highend systems now need to be Single +12V Rail PSU's.
Please note that the Seasonic built Corsairs & Antecs (HE & Trio) are, regardless of advertising,
Single +12V Rail PSU's, in that there is no per-rail current limiting, meaning that any +12V rail can pull whatever +12V amperage is available. This is also true of the Seasonic M-12's.
The Corsairs are built to higher standards than the Antecs.
From PC P&C's Power Supply Myths Exposed!: http://www.pcpower.com/technology/myths/
8. ARE MULTIPLE 12-VOLT RAILS BETTER THAN A SINGLE 12-VOLT RAIL?
With all the hype about multiple 12-volt rails (ads claim that two rails is better than one, five is better than four, etc.), you’d think it was a better design. Unfortunately, it’s not!
Here are the facts: A large, single 12-volt rail (without a 240VA limit) can transfer 100% of the 12-volt output from the PSU to the computer, while a multi-rail 12-volt design has distribution losses of up to 30% of the power supply’s rating. Those losses occur because power literally gets “trapped” on under-utilized rails. For example, if the 12-volt rail that powers the CPU is rated for 17 amps and the CPU only uses 7A, the remaining 10A is unusable, since it is isolated from the rest of the system.
Since the maximum current from any one 12-volt rail of a multiple-rail PSU is limited to 20 amps (240VA / 12 volts = 20 amps), PCs with high-performance components that draw over 20 amps from the same rail are subject to over-current shutdowns. With power requirements for multiple processors and graphics cards continuing to grow, the multiple-rail design, with its 240VA limit per rail, is basically obsolete.
PC Power and Cooling is once again leading the industry. All of our power supplies now feature a large, single 12-volt rail. The design is favored by major processor and graphics companies, complies with EPS12V specs (the 240VA limit is not a requirement) and is approved by all major safety agencies such as UL and TUV.
From Silverstone: http://www.silverstonetek.com/products-da750.htm
"With the knowledge that single +12V rail power is the next generation power supply, SilverStone Technology introduces Decathlon series, offering enthusiasts more choices with single rail power selections to handle their system."
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FSP Group (Fortron Source) BoosterX 3, 300W SLI Graphic Power Supply
Dedicated Multi-GPU Graphic Power Supply Unit
Specs: http://www.fspgroupusa.com/FSPNEWS/BOOSTERX3.asp
From $66: http://froogle.google.com/froogle?so...line&scoring=p
If you have a good PSU, but need more power for SLI,
just put this +12V (only) GPU PSU in an empty 5.25" bay!
Jason's (EOC) Reviews: http://www.extremeoverclocking.com/articles.php#13
jonnyGURU's Reviews: http://www.jonnyguru.com/reviews.php
Legit Reviews: http://www.legitreviews.com/articles/power_supply/
Nvidia SLI Certified: http://www.slizone.com/object/slizon..._powersupplies
For more information: http://forums.extremeoverclocking.co...2&page=1&pp=20
Updated 3-16-07
Dave  
Last edited by davidhammock200 : 03-16-07 at 09:15 PM
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