about "multi-rail" supplies

[sluggo]

Not exactly true.

 

Although common voltage/current source, independant current limiting, voltage regulation and filtering are all possible and are offered to one degree or another on many "multi-rail" PSU's.

 

Dave

I've spoken to a couple of other folks on this since I first posted. One claims that he's tested supplies that do have independent current limiting for each rail but could not recall the models. In any case, what I should have perhaps said was "all the "multiple-rail" designs that I've seen are just single rail supplies".

 

Anything is possible, but independent regulation would raise the cost of the supply significantly, and as far as I know only the Enermax Galaxy line ($300+) offers independent regulation on even two of it's outputs, much less the three or four "rails" shown on some supplies. I'll continue to test new supplies as I get them and will try to remember to post here when I see something new. Cheers.

[Yellowbeard]

As I understand it, the seperate rails are also supposed to be a point of over voltage protection to guarantee that no particular area of the system can draw any more power than that rail can provide. But, with the power hungry systems we have now, this can be a double edged sword as you will have a circuit capping the current on a rail supplying a component (8800GTX anyone) or components that need more current than that rail can supply. Then, load balancing comes into play........:confused:

[HITandRUN]

As I understand it, the seperate rails are also supposed to be a point of over voltage protection to guarantee that no particular area of the system can draw any more power than that rail can provide. But, with the power hungry systems we have now, this can be a double edged sword as you will have a circuit capping the current on a rail supplying a component (8800GTX anyone) or components that need more current than that rail can supply. Then, load balancing comes into play........:confused:

 

... thats why 1 rail and massive amps will always win! At least in my book! There is no capping and reducing of one rail because the other one wants more juice. One rail and enough Wattage and Amperage should do it! High live PC Power & Cooling who can afford it. He He!

[Yellowbeard]

... thats why 1 rail and massive amps will always win! At least in my book! There is no capping and reducing of one rail because the other one wants more juice. One rail and enough Wattage and Amperage should do it! High live PC Power & Cooling who can afford it. He He!

 

As I said, that is where the load balancing comes in. If a PSU can properly load balance, there is not problem with multiple rails. And proper cabling helps also.

[HITandRUN]

As I said, that is where the load balancing comes in. If a PSU can properly load balance, there is not problem with multiple rails. And proper cabling helps also.

 

Agreed!

[davidhammock200]

Right now, at least for highend gaming systems, a large single +12V rail is the best way to go!

 

The PC P&C 1KWSR being the best example with +12V@72!

 

Now the PC P&C 750W, 610W, the Corsair 620W, 520W & most of the new Seasonic's

allow any "rail" to have whatever it needs, so these are really single rail PSU's for our purposes,

regardless of advertising.

[Fum]

I am confused? :confused:

 

From PC Power & Cooling:

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.

 

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

 

If in fact power is trapped, then how can we be secure just adding up the multiple rails?

[davidhammock200]

From: Dave's Short List: http://forums.extremeoverclocking.com/show...6&postcount=192

 

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."

[Yellowbeard]

PC Power and Cooling makes good PSUs. However, that info is dated or simply misleading and is more along the lines of marketing as opposed to factual data. Here's a good read:

 

http://www.hardforum.com/showthread.php?p=...#post1030579230

[Astennu]

I have found a PSU that also has 3 transformers. Its the Coolermaster Realpower 850:

 

http://www.neoseeker.com/Articles/Hardware...emba_psu/3.html

 

I guess the two big transformers are the for the 12v lines. I have send a e-mail to coolermaster to ask if it has real split lines like the Enermax Galaxy:

 

 

And here you have a Pic of a OCZ GameXStreme 850w:

 

http://www.neoseeker.com/Articles/Hardware...850w_psu/3.html

 

With this info found i wonder why the Coolermaster Realpower Pro is not reccomanded in use with DFi Boards. Can anyone awnser that question ?

[davidhammock200]

IMO:

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."

Dave :angel:

[Astennu]

You also said that a Corsair PSU has 2 Lines on paper but actually has one line.

 

The Coolermaster PSU has 6 lines on paper so its possible thats its the same as the corsair in that way and that i would have combined lines.

 

But i have read that the Galaxy is a PSU that really has 2 separate lines. 34a and 43A. ( thats what i found in Sluggo's topic ). And The coolermaster also has two of these transformers. I really wonder what reply i will get from coolermaster. I suspect that they wont tell.