QUOTE(irangan @ Mar 10 2007, 07:33 AM)
Guys, I been reading alot of article about PSU 12v rail stuff and in the end I still confused as before.
I am not quite sure what is the difference between single rail and double or even quad rail PSU.
According to some article, they said single rail psu kinda of old school stuff and most of those latest gadget at least dual rail to operate properly as the second rail will provide 'cleaner' power to hardware.
Some article said that single rail PSU is very useful those noob like me that dont know how to balance those multiple rail.
Conclusion, I am confused. Abang sniper69 said 560w Silverstone Zeus 560w 38a single rail is very good. But I saw a Tagan Dual Engine 600w, written on the PSU, 48A quad rail, TG600-U25 and was very interested in that.
But if I really to 'balance' the quad rail, i will go for SS Zeus because I know nut about electricity stuff. So what do you guys think? thanks ya
ok, i know there's a lot confusion here
, anyway... i'd take PC&PP, Silverstone (Olympia & ST56ZF) highest end PSU for instance - what in common...? it's single rail
, i'm not saying that dual-rail, tri-rail, quad-rail or even 5-rail (Enermax) aka multi-rail is not good, but as for my preference, i will not go for multiple rail, why? simple, multiple rail isn't good as single rail
...i'd take for an example, 80A on Quad Rail isn't really 80A, 80A on Single Rail is exactly 80A or even higher (Silverstone Olympia 1000W) claimed peak 88A. this same goes to PC&PP.
Extreme Overclocking - Dual Rails, The True StoryPC&PP - Power Supply MythsQUOTE
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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.
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* Some PSU makers are using 12V2 to supply more than just the 2x12V or 4x12V connectors. It is often used to power the 6-pin 12V PCIe outputs as well.
* Many PSUs marked as having dual (or more) 12V lines actually have only a single 12V line - they do not feature two 240VA current limiters specified by ATX12V v2.xx; they have only one Over Current Protection (OCP - current limiter) for the single 12V line.
* The 240VA current limit is considered a high cost, useless annoyance by most PSU makers. If multiple 12V lines are used, because the vast majority of components now use mostly 12V, the 18~20A limit for any line means that the precise power distribution to the various 12V output connectors can become critically important in some cases.
* The engineers point to the many high power pre-V2.xx ATX12V PSUs that had as much as 30A on a single 12V line. As a product class, those have not proven to be any more dangerous in any way than other ATX12V PSUs. Even if exceeding 240VA in a single wire run was dangerous, this is extremely unlikely to occur in a PC because 12V is distributed to many different components on many different wire runs.
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What does all this mean? The safety benefit of dual 12V lines is questioned by the engineers I spoke with. There are many downsides to multiple 12V lines, including higher cost and the extra headache of ensuring adequate 12V current for all the components in complex, high power systems. For the consumer who is trying to make a choice among the myriad of PSUs available on the retail market today, the most practical approach regarding dual 12V lines and power capacity is to consider only the combined 12V current capacity.
i hope it clear you guys a bit
Added on March 10, 2007, 12:40 pmQUOTE
Why did multiple 12V rails come about?
Multiple rails came about because the EU mandated that the power on a single rail should not exceed 240VA (12V x 20A). Intel then stipulated in the ATX12V v2.xx standard that if the power on a 12V rail was likely to exceed 240VA, a second 12V rail needed to be engineered. For practical purposes, a limit of 18A was used, allowing for 2A headroom. Manufacturers replied by mass-producing multiple rail power supplies, using several types of engineering. Some power supplies are well engineered, and the 12V rails are truly separated with separate transformers. However, others draw power from one single transformer and the rails are only separated after transforming takes place. The issue with multiple rails is that the power per rail is relatively low, which unfortunately often results in the use of inferior parts.
Do we really need multiple 12V rails?
The answer is simple: no, we do not. As stated above, there are high-end power supplies with one single 12V rail that are SLI certified. These single 12V rails are rated at >30A, and thus likely build with high-quality parts. This is also confirmed by Intel, who unofficially dropped the 240VA standard in spring 2005, actually re-instating single 12V rail power supply units as an accepted standard. It is interesting to note that the Siverstone SST-ST56ZF 560W (single 12V rail, 38A) is SLI certified for Dual GeForce 7900 GTX or Dual GeForce 7800 GTX 512 MB, while its "bigger" brother, the Silverstone Zeus SST-ST65ZF 650W lacks this certification, although it is certified for all other SLI configurations and delivers 42A on the combined 12V rails. The problem likely is that it has a bit of an odd distribution of current along quadruple 12V rails (13A, 18A, 16A, 8A). Thus, this is an example where the single rail PSU is preferable over the multiple-rail PSU. On the other hand, there are many really well engineered and well built multiple-rail PSU. This FAQ is only meant to point out that multiple rails are not a necessity for a good PSU.
taken from :
Do You Need Multiple 12V Rail?This post has been edited by sniper69: Mar 10 2007, 12:40 PM 
Jan 19 2007, 10:38 PM
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DROOLLLL.. okayla, now i feel like driving to Subang and get one from Moderno! I think they must have made a refresh/updated for the ST56F. Weird that its not stated in their website or any where else.
, it's at least 36A
what do you mean by that? 24 pin on PSU or 24 pin on mobo? i assume, PSU comes with 20+4 pin, 4 pin (CPU) 
)
... i actually want to ask same Q though...
, or else, you might end up blown PSU or "unbooted" PC 
, i thought, you're using X1950? but still you're going to need >500W, 400W is like meet the minimum requirement, your 400W PSU might be in stress
, me myself recommend this PSU too 
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