modular and multi rail is not recommended according to PC Power and Cooling? (http://www.pcpower.com/technology/myths/ - 1st page link) hrmm..... the 1st page of this thread has 5 links so far. the 1st two is suggesting LYN forumers to follow the tier guide of XS and Jonnyguru (it's without h actually and actually he is kinda pissed if ppl miss-quoted his name). while the 'Power Supply Myths Exposed' guide from PC Power & Cooling suggested that multi-rail and modular psu should be avoided. let's see how jonnyguru think of modular and multi psu. it seems to be kinda contradict from jonnyguru point of view compared to PC Power & Cooling. so which one to trust? your pick. if you're a follower of PC Power & Cooling, you should follow
davidhammock200 PSU Guide instead of jonnyguru's.
http://www.jonnyguru.com/forums/showthread.php?t=1036QUOTE
Picking the right power supply
Resistance: Modular connectors, adapters and splitters.
Years ago, there was this cat named Ohm and he explained to us that resistance sucks.
Ohm’s law as it pertains to resistance in electrical current is R (resistance) X I (current) = V (voltage.) So you can see, the greater the resistance, caused by either length of wire, gage of wire or having to go through connectors and/or the greater the current, the less voltage you get.
In simple terms, having a modular power supply may drop your voltage a little because of the resistance between the modular interface and the cable. And using a 20-to-24 pin adapter or any kind of splitter can cause a slight drop in voltage because of the resistance caused by any imperfect contact between the pins of such an adapter or splitter. But on that same note, every single connection you make (PSU to drive, or motherboard, or video card) is another connector that is going to create a little more resistance.
There’s been a lot of scare tactics used to convince people to not go with a modular power supply. But the reality is, even at high loads the resistance is quite minimal if the correct measures are taken. For example: A PCI-e cable is going to have less resistance if there’s 3 12V leads on each side of the cable and 3 grounds on each side of the cable. Unfortunately, some modular power supplies may only have one or two wires split into three for each row for a PCI-e connector. Some homework needs to be done on how the cables are constructed when considering a modular power supply.
And when using a modular power supply, adapters or splitter, make very certain that the connection between both interfaces is secure, firm and flush. Make sure all of your connectors are fully seated. This goes for standard power supplies and the connections you make to the motherboard, your drives, etc. as well. Because if you have a connector that is not fully seated, you create resistance. That resistance not only can cause a drop in voltage at the end of that particular wire, but also create heat. I’ve actually seen BURNT connectors from cables not being plugged all of the way into their sockets.
One last thing; Gold plated contacts. They don't do any good unless they're interfaced with gold plated connectors. In fact, the mating of dissimilar metals is actually more prone to corrosion than if both connectors were tin. So if you get a modular power supply with gold connectors, keep in mind that it may be better to have gold only on the power supply side where the modular interfaces are also gold plated, but not on the component side. I haven't seen hard drives and motherboards with gold plated power connectors.
UPDATE: In PC Power and Cooling's "Power Supply Myths exposed" they state that "the voltage drop can be as much as would occur in 2 feet of standard wire." Actually, two feet of wire don't present much resistance. But they do make the point that they may "can easily loosen, corrode, and burn." That should read, "corrode or loosen and burn." Fears of corrosion are rather unrealistic. A power supply connector has as much chance of corrosion as any other contact point in your PC. Your video card? Your RAM? Even the connectors to your drives, motherboard, etc. Obviously, when you double the number of connectors you double the chance of corrosion, but unless you live on a House board, corrosion is rare. The loosen and burn I explain. Solution: There's no reason to keep unplugging and re-plugging your power connectors. Make sure they're in tight and leave 'em alone.
QUOTE
Picking the right power supply
So why do they split up 12V rails?
With the demand on +12V becoming greater and greater, Intel decided it would be "safer" to split the duty of supplying +12V across two rails. It's "safer" because inexpensive transistors capable of supplying more amperage (say more than 34A) at any kind of decent efficiency (70% or better) are subject to blowing up. I guess that's not very “safe.” ;-)
To split the duty up between two (or more) +12V rails, one can use cooler running, cheaper transistors to supply the power. Furthermore, this isolates devices on one rail from another, so EMI introduced by lighting inverters and drive motors can be isolated from sensitive components like the CPU and video card.
Some people have questioned the principle of multiple 12V rails.
And for good reason! But I don’t think multiple 12V rails in general should be shunned. But it’s best to know what rails go where when considering using a multi-12V rail power supply with a high end system.
ATX specifications only say that the CPU (the 2x2 4-pin connector) is put on a separate rail from the ATX connector (the 20 or 24-pin) and the drive (also used for fans, lights, etc.) power connectors. They also specify that no one rail should have more than 20A available on it (that’s their “safe” limit, so to speak.)
So if you breeze through reading that, you would say “Ok. The CPU gets it’s power from the 12V2 and everything else gets it’s power from the 12V1.” But then you realize there’s a problem with that. 20A for just a CPU, even a dual core or even a dual CPU, is overkill. And 20A may be enough for some drives, lights, fans, etc. But what about PCI express video cards that regulate their voltage from the 12V rail via an auxiliary 6-pin connector? High-end video cards can easily tax 7A or more EACH off of the 12V rail. 20A leaves zero overhead.
Unfortunately, some power supplies adhere to the “quick read” version of the ATX standard and put everything but the CPU on one rail. This is where everyone seems to be running into problems. Fortunately, some other power supply companies have gotten creative with rail distribution. I’ve seen power supplies with the PCI express connectors on 12V2 and even some with one PCI-e connector on each of the two 12V rails. THESE are the kind of dual rail power supplies you need to look for.
Some power supplies have more than two rails. The Antec NeoHE, for example, has three. Two modular connectors are labeled for 12V3 use. These are the two ports one should plug their PCI-e connectors into. Other power supplies have four 12V rails. These typically adhere to a standard other than ATX called “SSI” but PCI-e is taken into consideration by keeping the PCI-e off of the same rail as all of the drives. Even if a PCI-e is plugged in using a typical drive Molex, that rail is still separate from the ATX connector, and the 2x2 4-pin connector.
http://www.jonnyguru.com/forums/showthread.php?t=1701QUOTE(jonnyguru)
A PSU that adheres to the SSI specification will have each of the two CPU cores on it's own rail. So let's say +12V1 and +12V2. The motherboard and peripherals (including PCI-e) will be on +12V3 and +12V4.
Most PSU's built for gaming rigs put each PCI-e on it's own +12V rail and adhere to an ATX12V specification for +12V1 and +12V2. For example: CPU on +12V1 and the ATX and all peripherals on +12V2. This is how the OCZ GameXstream and Ultra X-Finity 800W are.
I think the post is full of a lot of generalizations a kin to posts like the ones that tell you what brand PSU's to avoid. Multiple +12V rails have it's benefits and can provide enough power to all peripherals if laid out correctly. Just because PC Power & Cooling and Silverstone don't know how to adhere to ATX12V and SSI guidelines and distribute power for a typical gaming machine doesn't mean that all three, four and five +12V rail PSU's should be avoided
QUOTE(Kab)
Intel ATX12V Version 2.0 started recommending dual +12V lines that can deliver upto 20A at +12V - i.e. Version 2.2 Revision 1.0 June 2006, 3.5.7:
"The 12 V rail on the 2x2 power connector should be a separate current limited output to meet the requirements of UL and EN 60950."
(Low Voltage Directive (LVD) 2006/95/EC ): If it meets that, it displays the CE mark.
EN 60950-1/IEC 60950-1, UL 60950-1 are safety related directives, one of the requirements being that not more than 240VA is carried on any wires or exposed traces in such ITE because its the max recommended for an electronic device that a consumer will have the chance of access to (EN 60950 provides high level of protection for equipment designed for use with a voltage rating of between AC 50 and 1000). Overcurrent can also occur due to short circuits on the connected system and OCP on any rail acts as a safety net in place for the PSU and other attached components.
You'll find more on them all here:
http://www.itesafety.com/history.htmHere's a typical EN 60950 test report for a Rack-Mount Front Ends SMPS:
http://www.power-one.com/resources/p...cyapproval.pdfHere's its spec:
http://www.power-one.com/resources/p.../fcp600_48.pdfNow to work around this because its a PITA, costs more and manufacturing engineers thought there wasn't really any benefit or danger, with 30A plus +12V before Intel's ATX12V rail limits; PSU engineers often left one actual +12V rail which further branched into a few (2-5) +12V rails and many without current limitations...
- because that could cause PSU shutoffs on system arrangements that suck more VA on any one +12V more than where the OCP is restricted to (so) that would hinder the chances of the PSU being favored for reasons other than product quality,
- is difficult to balance out the distribution adequately for every possibly setup beforehand,
- and it was done as a flexible safety net to allow a few VA over the +12V 240VA limit, as its the most needed voltage rail and many setups may exceed over the limit at any one high stress moment but not for continuable sustained operation nor on other rails
This is what someone at AMD and SeaSonic both told me in essence, who I've known for quite a while now (+7 years). None of this means I'm going to take a radical approach and ditch single rail or multi railed PSU's. Even though I recall AMD fanboys in particular had the hardest time accepting multi-rails and defending single rails "just because" Intel seemingly stipulated this directive, there's no real reason to favor one over the other and I've ran both perfectly and so have the majority. So I'll stick to that as long as the PSU is of satisfactory service
SSI EPS12V 2.91 covers 550Wplus and mentions i.e.:
"The +12V rail may be separated into three +12V rails to meet regulatory requirements for energy hazards (240VA)."
AND this is what users would be better off recommending rather than some ideology with no substance-
How to test a PSU efficiency:
http://www.efficientpowersupplies.or...tocol_R6.1.pdf
, none of them is good 
Wonder though, how much would a crossfire/SLI setup take?
