Indeed, looks like just the laws of physics going on here. I think it's funny OCZ will use that as another marketing tool.

Newegg $130 S12 Energy+ 550 http://www.newegg.com/Product/Product.a ... 6817151027

Newegg $140 M12 500 http://www.newegg.com/Product/Product.a ... 6817151029

Might be in fact that Seasonic's design has only one rail and not separate rails despite of sticker saying otherwise.

Johnyguru's review of Corsair mentioned that there's only two "rails" on main PCB:


One French review of M12 also mentioned that there's just two "rails" on PCB and showed pic of that part.

Now PC P&C Silencers have officially one big 12V rail and they use entirely same internals with "two 12V rails" on PCB.
http://www.pcpowercooling.com/products/reviews/oc3d-2/20151352146l.jpg
http://www.pcpowercooling.com/products/reviews/oc3d-2/index.html

So looks to be propable that neither these new Seasonics care about different rails.
That would well explain why I haven't gotten any answers from Seasonic about distribution of 12V rails.

I just got my M12-600 and here are a couple thoughts:

1) The 120mm fan is quiet, although my old Antec TPII-550 with a YL fan-mod was smoother sounding. This fan is exactly what was in the older 500-600W models

2) The 60mm fan never runs (though it is in a P180 case) - at least not so far, so I can't comment on it's acoustics.

3) No problems starting up.

4) The modular connectors are quite nice; Decent "snap" when they get seated into place.

5) Votages are right on (measured with a DMM): 3.3V is dead on, 12V is a little high (12.1V), but not uncommonly so, and 5V is dead on 5V.

All-in-all it's everything I was hoping it would be.

*waits for SPCR review of the M12 and S12+*

I installed my M12-500 couple days ago.

Confirm 2, 3, 4. I don't have the tool to check 5 and I didnt ply open the PSU to check 1.

The PSU has the same noise profile as my SS-380W.

It came with plenty of cabling for my needs, and have 2x 2 and 2x 3 4pin molex cables and plenty of SATA power cables.

It's a shame that they don't make a 300W model.

i was wondering to get this or the corsair

12V1
12V2
12V3
12V4

I went to the Seasonic site and could not find info on.. anyone know how the rails are divided up?


Thanks!

Mike

Here is what you need.
Stay tuned for jonnyguru's review on M-12 700.
For now some pictures. Magically those four rails are two.

The jonnyGURU "review" and pics are very interesting...

The new ATX12V spec (whatever it's called, exactly) requires that the 4pin processor 12V connector be on a separate "rail" (i.e. separate over-current regulator), so there has to be at least 2 12V "rails" in any ATX12V supply that can provide over 20A (240W) on the 12V line. The fact that the modular connector board has only a single 12V "trace pad" does not mean anything; what matters is the amound of current that the wires feeding it can supply. If those wires are coming from 2 or 3 "rails", then you could potentially draw 18x2=36A or 18x3=48A from all the lines connected to that modular PCB, assuming each "rail" is limited to 18-20A.

My guess is that the 12V "rail" that feeds the processor is exclusive to the 4-pin ATX12V and 8-pin EPS12V connector, and has a standard 20A limiter. The 12V line that goes to the 24-pin ATX connector is a separate "rail" from that one, and it looks like it might also go to the modular connector board.

Then the question is whether there are really 2 other "rails" for the modular board, or if that 2nd rail doesn't actually have a 20A limiter. Is the limiter put someplace else? Is there any current limiters on the modular PCB? If there are really 2 other current limited "rails", it looks like they feed exclusively to the modular board.

My guess is that they are "cheating" a little and actually have one current limited rail, and another non-limited rail, or technically limited to the equivalent of 3 rails - i.e. 54-60A, which is more than the PSU can produce.

Can anyone either confirm or deny this speculation?

Well, this is what I found myself...

http://www.jonnyguru.com/PSU/HX620W/index2.htm

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.


More info

http://www.hardwaresecrets.com/article/371/5

Exactly.
And PC P&C Silencer which is made by Seasonic basing according to XS is officially one rail design and its insides are identical (except heatsinks) with two groups of 12V wires in PCB.

http://www.pcpowercooling.com/products/reviews/oc3d-2/index.html

Based on all the data available, this is what I think:

- The main PCB has just 2 12V "rails"
- Neither of the 12V "rails" has a 240VA over current limiter ("OCL") - then what exactly separates them?
- Each of those 2 rails splits to 2 separate "fake rails" (separate only in the wires conecting them)

PCB_12V1 -> 12V1: ATX 20+4
PCB_12V1 -> 12V2: PCI-e 1 and first two peripheral connectors
PCB_12V2 -> 12V3: PCI-e 2 and last three peripheral connectors
PCB_12V2 -> 12V4: 4-pin +12V and 8-pin +12V

Personally, I don't necessarily like the OCL - it makes load balancing more difficult. That said, I wonder how Seasonic can get away with calling this an ATX12V 2.x compliant PSU when it doesn't have the OCLs...

Agreed.

But there is one reason to think that there is some kind of separation between 12V1 and 12V2: look at Test 5, 12V readings here: http://www.jonnyguru.com/PSU/HX620W/index2.htm .

The fact that 12V1 does not show the sawtooth "ripple" under load that is present in 12V2 and 12V3 - even though supposedly being drawn from the same 12V rail - makes me think there is some kind of isolation or separation between the 2 rails.

It was looking and this data, and how jonnyGURU loaded the supposed rails, that I came up with my assumed connection scheme (in the post above).

Then again in review of 520W Corsair which has identically "three rails" there isn't any difference in ripple between "rails" and:
Outside of a few traces zig zagging across PCB, I couldn't find how even 12V1 and 12V2 are separate



Don't ask, looks like even Seasonic doesn't know that because I've twice asked it from them and never got any kind answer.

I explained that away by comparing how he loaded each supposed rail (they were slightly different) in both Corsairs:

Assumed connections:
PCB_12V1 -> 12V1: ATX 20+4
PCB_12V1 -> 12V2: PCI-e 1 and first two peripheral connectors
PCB_12V2 -> 12V3: PCI-e 2 and last three peripheral connectors
PCB_12V2 -> 12V1: 4-pin +12V and 8-pin +12V

620:
"12V1" main ATX connector and a couple of the Peripheral connectors (12A PCB_12V1)
"12V2" 8-pin EPS+12V connector (12A PCB_12V2)
"12V3" peripheral connectors and the PCI-e connector claimed to be on the 12V3 rail (15A PCB_12V2)

So that's 12A on PCB_12V1, and 27A on PCB_12V2

In addition: 10A/20A on 3.3/5V

520:
"12V1" main ATX (12A PCB_12V1)
"12V2" a load on the PCI-e connector on what is supposedly "12V2" (12A PCB_12V1)
"12V3" and a load on what is supposedly "12V3" (12A PCB_12V2)

So that's 24A on PCB_12V1, and 12A on PCB_12V2

In addition: 8A/10A on 3.3/5V

Comparaing the 620 to the 520, in addition to 27A vs 24A on a single "12V" line, the 620 is being loaded by about 57W more on the 3.3/5V lines. Assuming the circuitry is essentally the same, that extra 90-100W being drawn from the 620 could cause the ripple shown.

At least that's my story and I'm sticking to it!

IIRC, Intel has long unofficially waived the OCL as a part of the ATX12V standard for at least a year now...

I personally haven't read that, although I could certainly be true.

Then if true, I wonder if we will return to true single 12V rail PSUs soon, or is there enough misinformation out there that says "more rails are better" that we will still have quad-rail PSUs?

Regardless, so far I am very happy with my M12-600.

It's been mentioned in the power supply recommendations info on this site as well. Quoted from the page: "What's really interesting is that Intel has tacitly waived the 240VA limit requirement in its PSU validation program"

I'm of the opinion that we don't really need multiple rails internally. The whole point of the spec was to reduce the total output on each line going out. As long as we don't have a lot of ripple or voltage drop on the psu under various conditions, I'm fine with a single rail. It's definitely ATX 2.x in intel's eyes and that's good enough for me.

The Intel list is here: http://www.intel.com/cd/channel/reselle ... /35815.htm
AcBel, Antec, Enermax, Jou Jye, Seasonic , Sirtec, Superflower, and HEC are among >240VA brands. If Intel tested all the PSUs claimed to be ATX12V 2.x, the list would be much, much longer.

JonnyGuru has his review up. Looks great except for the price:
http://www.jonnyguru.com/

I actually bought one because my local Fry's only had the 700W version and it was "only" $189 (quite a bit cheaper than online, especially with shipping), and I decided to splurge on something that will probably be a 5 year investment.

Haven't installed it yet...

Here is the final peice of the puzzle:

"What Seasonic tells me is that there was an issue with high end video cards overloading a single 12V rail. So with Intel's blessing, Seasonic removed the OCP. Technically, Intel has removed the 240VA rail limit from the ATX12V specfication (although I've yet to see this published on FormFactors.org), and the UL simply considers devices with single output leads with output capability greater than 240VA (12V @ 20A) a different product class (level 6 instead of level 3.)"

The M12 seem to have a smaller open arera on the back plate than the S12E+. Closed around the AC connection and power switch.
Any idea why? Seems a bit strange to me.

This is just a guess, but maybe it's because the 60mm fan changes the airflow in such a way so that particular exhaust area isn't used much or isn't needed?