I dont know if this is common knowledge - but I came across this and thought peeps here may want to see this if not yet known.
The 3 rails on a Corsair PSU…
I don’t know whether this SMPS is really with 3 rails or not, but I have seen SMPS with 3 to 4 rails. Most probably that was 700W or 800W Gaming SMPS.
I saw in a site as AD-Banner with a 8800GTX 4-SLI review or with the PSU Calculator.
All seasonic multirail PSUs actually act like a single fat railed one. I know cos my NeoHE does and this corsair is also a Seasonic OEM and I guess it should also be the same.
From what I have read in the reviews the Corsair 620w PSU is the same as a Seasonic S12 …
BTW … I got this picture from the Corsair forums.
I don’t know whether this SMPS is really with 3 rails or not, but I have seen SMPS with 3 to 4 rails. Most probably that was 700W or 800W Gaming SMPS.
Lol u r confused.
Anyway the rails are actually advertised to comply to Intel Spec of ATX 2.04 which cant cross 240VA on a single rail 
Nahh my NeoHE is a 3 railed PSU at 500W.
That Corsair too is tripled railed and performs like the NeoHE as Chaos mentioned.
@ Eazy - Yeah, the HX620 is a Seasonic S12 
It acts like a single rail PSU, any rail needing more then +18V will get it, no Over Current Circuit protection is present…
So thats why we have rails, always wondered why single rail PSU’s arent the In thing these days…
I think it can.:S
Single rail PSUs are the in thing again- quite opposite to the anti-single rail propaganda a couple of yrs back.
Check most new 750-850W+ psus coming out now.
And after drooling over multi rail, esp dual rail psus and getting one, i read this some months back and was i amused.:lol:
Silverstone DA850 >
Introduction
With the knowledge that single +12V rail is the way for next generation power supply, SilverStone Technology continues the expansion of Decathlon series power supplies, offering enthusiasts more flexible and greater output choices to handle their system.? The Decathlon DA850 power supply hosts a full array of amenities such as quad PCI-E connectors, 100% modular cable system, bigger and quieter 120mm cooling fan, while still maintaining a typical efficiency of 80% and better.? All these combined with powerful 70A single +12V rail output gives DA850 the power superiority in its class.
- The all-around single +12V rail output power with advantage of 100% modular cable system!
SilverStone Technology Co., Ltd - Designing Inspiration
I am sure all have seen this but still …
EXCELLENT Strip down at H/W Secrets >
(Please go through the entire thing from page one- good peek at understanding psus imho)
What immediately caught our eye were the three separated +12 V lines listed on the label (see Figure 17). As it happens to all high-power units nowadays, Corsair uses a “virtual rail†concept, where they label their power supplies as having separated +12 V rails but inside the unit they are all connected together to a single +12 V rail on the power supply printed circuit board. Unfortunately all manufacturers seem to be doing like this to match the ATX12V 2.x and EPS12V specifications, which require the power supply to have separated +12V rails.
Inside this power supply, however, the wires are separated into only two virtual rails, and not three, see Figures 18 and 19. These two virtual rails are connected the single +12 V power supply rail, as shown on Figure 19 (the red lines are jumpers, i.e. wires). Two groups of wire are connected to +12V1 and three groups of wire are connected to +12V2 (see Figure 18).
For this, Corsair sent us this explanation: "Since our PSU follows the latest Intel design spec, it is consider an UL Level 6 design, which means there is no 240VA limitation on the +12V rails. In addition, all the +12V rails are drawing from single transformer, the rail separation is not done on the PCB side, but on the wiring side. Therefore the +12V1 and +12V2 you see on the PCB doesn’t really mean anything.â€
We do not agree, since if we used “wire groups†as a new definition for “virtual railâ€, this power supply would have five virtual rails (as this power supply has five groups of +12V wires) and not three. In both cases the label is wrong.
From the previous page we came with some maximum theoretical numbers for the +12V output (1,440 W), +5 V (300 W) and +3.3 V (99 W).
As we mentioned earlier the maximum current/power each line can really deliver will depend on other components, especially the transformer, the coil, the capacitor and the wire gauge used.
For the +12 V output Corsair stated 18 A for each one of the “three†virtual rails. This would give a 216 W per rail or 648 W. But, as we mentioned, internally this power supply has only two virtual rails, not three. If we assume each one can deliver 18 A, this gives us 436 W total – which is far more plausible that the 600 W printed on the label. If you add 170 W (3.3 V/5 V) + 436 W (correct 12 V output) + 9.6 W (-12 V) + 15 W (+5VSB) you get 630 W.
For the + 5 V output Corsair stated a 30 A maximum current, which translates to 150 W, while for the +3.3 V output the manufacturer stated a 24 A maximum current, or 79.2 W. On the label, however, Corsair says that the combined power of +3.3 V and +5 V outputs is of 170 W (since they are connected to the same transformer output).
Anyway, all positive outputs are labeled with a current well below the maximum current each rectifier can deliver.
Unfortunately we don’t have the necessary equipment to make a true power supply review; we would need to create a real 620 W load to check if this power supply could deliver its labeled power or not.
Corsair HX620W Power Supply | Hardware Secrets
At Jonnyguru >
Since the review of this power supply, some interesting observations have been made of Seasonic built power supplies claiming to have three rails.
Below is a picture of the modular interface PCB. This would have you believe that three peripheral connectors and one PCI-e connector were on one rail (labeled 12V3) and the other two peripheral connectors and PCI-e connector were on another rail (12V2.) This would leave one to assume that the 4-pin and 8-pin are on 12V1 perhaps with the main ATX, or the main ATX is on 12V2 with the fewer number of peripheral connectors.
Looking at the Seasonic main PCB inside the Corsair PSU reveals only two rails, labeled 12V1 and 12V2. There is no third rail. This is illustrated well at Hardware Secrets. Although I can not say that these rails are or are not somehow electronically separated in the PSU’s circuitry somewhere, I did find that there was no OCP (over current protection or “limiter”) on either of these rails as I was able to load any given connector up 30 to 40A with no drop in voltage, system shut down, etc.
So it is my opinion that we essentially have a single 12V rail PSU here. Certainly there is nothing wrong with this given the problems high end video cards have had with getting enough power from a single 12V rail when the OCP is set to the typical 240VA limit. But we do lose the advantages of multiple rails such as protection from damage to one rail from a short on another and the simple “filtration” of noise introduced from one rail to another.
Quote:
Originally Posted by Supra View Post
Lol u r confused.
Anyway the rails are actually advertised to comply to Intel Spec of ATX 2.04 which cant cross 240VA on a single rail
I think it can.
Your own Corsair quoted statement below is negating that
Unfortunately all manufacturers seem to be doing like this to match the ATX12V 2.x and EPS12V specifications, which require the power supply to have separated +12V rails.
Actually if u read that Intel ATX12V 2.04 spec pdf,its done for our safety purpose only. Carrying too much current over a single rail can be hazardous
I cannot comprehend what you comprehend from my post or what you posted again.
I have just highlighted certain parts of the reviews and it is better to go through the whole of it coz sometimes 2+2 seems like 22.
All i said was-
(1) the HX620 seems like basically a single rail psu.
(2) You said that it is limited to 240VA limitation per rail which Corsair said it does not, i didn’t say that.
(The point is Corsair gimmicked the three rails part- if it is essentially a single rail psu like the reviewers feel- the question of 240VA per rail limit doesnt even arise).
(3) I am not saying buy single rail, most psu manufacturers are offering basically single rail psus in the 750-850W+ segment these days- especailly in the 1000W+ range.
(4) I said single rail seems the in thing again looking at the new single rail 850-1000W+ psus coming up- Deepak said ‘not in thing’ looking at the past 2 yrs odd.
And i still dunno how OCP(not Robocop OCP:P), allows more than 18v
like Deepak said- i think he meant 18A.
In fact, Jonnyguru did mention the good things in multi rail psus that we miss in single rail psus- if u read the last para.
The fact that it’s not safe to have very high amps running through a single rail is the reason why multi rail psus came into being- a reason why i said even i was amused to read that line on Silverstone site after drooling over dual rail psus for safety reasons all this while.
But the VA limitation made certain hi end cards, esp SLI seups suffer- so maybe thats the reason for the virtual rail concept and new hi end psus being single rail again.
IMHO, its a single rail psu with the internal circuitry designed such that peripherals connected get shared over 2 or more lines so that the current is distributed through those wires- but just in case one line draws more- it is not limited to 240VA.
This is elementary science of ‘parallel electrical network’- where at constant voltage and peak power, the amps get shared over the various branches as per the load on respective branches.
Lol …just confusion…anyway peace now.
Btw nice explanation
Lol..yeah meant 18A,
Also like you said Bikey, now a days most high end PSU’s have gone single rail style with virtual rails (the parallel circuit concept, where in current is divided at constant voltage), only thing is that there is no circuit present at these virtual rails to protect more then 240VA to pass through them, thus making them single rail PSU’s.
I am pretty sure other PSU’s (like the CM600 for example) have only 1 transformer giving +12V o/p to both the rails but the parallel virtual rails being prevented to draw more then the 240VA of ATX spec via OCP, need to do some digging to confirm it though. It just doesnt make sense to put in 3 transformers for the 3 +12V rails.
This, ladies and Gents is what we call a DOUBLE POST…
Why the hell do you have to double post ITFP..?
HX620W owner here. Testing it in office no buzzing, we use always on line interactive UPS’. But a CM 750 watt PSU showed some signs of buzzing.
Lol…double post just happened, like they normally do due to hitting the reply button twice or during server loads.