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help!! what is the advantage of a single rail high amp psu?

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March 8, 2007 2:34:57 AM

someone please explain this too me - i would real appreciate it!
March 8, 2007 3:41:19 AM

single rail gives power to all 12v components from one rail. so if a single rail psu has 35 amps and cpu requires 7 amps and gfx card 20 amps it can power them.

dual rail gives power from 2 rails. one is connected to the cpu only and the other goes to everything else. consider a 35amp dual rail psu which which has 18 amps per rail. it can power the 7 amp psu but not the 20 amp gfx card bcoz of the 18amp limit. 35 amp dual rail fails here where 35 amp single rail can do the job.

multiple rail is also similar. my thermaltake 750watt psu has 4 rails. it can supply maximum 60 amps and the rails have 18 amps limit.
March 8, 2007 4:15:38 AM

Thank you for response but most quad rails are triple cross connected - a pli-x line gets power from rails 2 3 and 4

in a quad sli with qaud rail

its like 2,3,4 2,3,4 for pci-x 1 and 2
then 1,2,3 1,2,3 for oci-x 3 and 4

with 12 line 1 powering the cpu and mob
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March 8, 2007 4:55:28 AM

Here is what PC Power & Cooling has to say:

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 this page:
http://www.pcpower.com/technology/myths/

Pretty much a load of marketing crap. But at least you can see one argument towards a single large rail.
March 8, 2007 7:08:36 PM

thank you for the info:

In the end i figured a good quad rail is cross connected in the case of a silver stone strider 750 the pci-x are connect to 3 (triple crossed) 12 volt rails.

i thought about getting the new silver stone single rail - i ordered the same quad rail psu 's i have been using since there is not reason not too - i saved $40 each. That is: $40 for 6 more amps in a single configuration

i used use the dual rail the new quad module is less expensive and has proven to work just as goo.
March 8, 2007 7:22:37 PM

pc power and cooling marketing -lol

i though about buying the $200 new pc p&c 750 watt unit then again silver stone is 80% efficient and module single rai is $20 less. But then again the stider is $60 less or $137 to be exact and works great and runs cool!

I have a quad rail strider running cross fire x1950's, 4 sata in raid 10/0, 2 gigs ram and the psu hardly gets hot!


energy get trapped? lol bs this mombo junbo might apply to some low end power supplies but this is mostly bs!

...> pure bs "a multi-rail 12-volt design has distribution losses of up to 30%" why do mult-rail psu's and single rail have the same efficiency rating?


this is strait off a web site! lol

most "good" multi rail psu's are cross connected - lol each line off the psu draws juice from 3 rails.

you never want to max out a psu anyways - i agree a single rail will allow you to get a little extra power if your system and your psu fit like a food and shoe. Most psu's are fit for 70-80% and they work better that way anyways!


"PC Power and Cooling is once again leading the industry"

they had come out with a $200 psu since there over priced $500 pcu is not much better then many costing half as much!



Quote:
Here is what PC Power & Cooling has to say:

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 this page:
http://www.pcpower.com/technology/myths/

Pretty much a load of marketing crap. But at least you can see one argument towards a single large rail.
!