How to know which rail in PSU powers what connections?

[RejZoR]

I'm wondering, how do you know which rails are designated to what cables on the PSU?
Especially when PSU has different amps on different rails.

For example, my current Be Quiet Dark Power Pro 11 PSU has 20A on first two rails and 25A on other two (total 4 rails).

I'm assuming the weaker rails are designated to SATA/molex power cables, potentially even P4/P8 and the stronger ones are dedicated to ATX/P8 and PCIe graphic card power connectors. Is my thinking correct or am I missing something?

 

[EarthDog]

Not sure. I would check the manual...

Doesn't it have the ability to switch to one rail anyway... or is that only on the 850W model?

That said, the values on there are pretty high, and I am ASSUMING those values are OCP limits. So it really doesn't matter what goes on what....within reason. Your logic is sound, so I would imagine that your theory is true.

Also, wow. $180 for a 750W PSU? I know these are solid units, but hell. You can have an EVGA that is just as good or better for $130 (after MIR) with a 10 year warranty. Damn.

 

[RejZoR]

Yeah, I checked the manual, it doesn't really say what rails are used for what. Also yeah, those are probably OCP limits.

As for the price, it seems better quality than many others, especially from the fan perspective which has FDB bearing and is really dead silent. I really wanted that and I was willing to pay premium for that.

 

[EarthDog]

You paid a hell of a premium for a fan. That EVGA is dead silent... in fact, its fan is OFF until a specific temperature/load. Particularly since you are only using around 400W in the first place you would never hear the fan on it. You could have easily used Be Quiets! 550W model and saved $50 (unless of course you plan on adding another card). But damn, $150 for a 550W PSU.. Just wow. Nice units, but not remotely worth the price considering the EVGA G2 and P2 units with their longer warranty (double @ 10 years), same/better quality. Oh well.

 

[MIRTAZAPINE]

I use the EVGA 1000w p2 it is silence even with fan spinning but most of the time the fan is off. It would only turn on when the Psu is at 50% load or it touches 50 celcius in temperature which for me never happen as I overkill it for my rig. I am a fan of having good Psu. If there is an EVGA Rma centre near you the 10 years warranty would be great!

 

[Vayra86]

Yeah, I checked the manual, it doesn't really say what rails are used for what. Also yeah, those are probably OCP limits.

As for the price, it seems better quality than many others, especially from the fan perspective which has FDB bearing and is really dead silent. I really wanted that and I was willing to pay premium for that.

That is really weird though. 20A isn't a very powerful rail if you run beefy GFX. That's only 240W. Definitely important info to know how the rails are divided.

UPDATE. Went through the manual real quick. Here is useful info. >>>

Overclocking Key
The Overclocking Key groups the individual 12V-rails to a single 12V-rail.
You can enable the overclocking function permanently by setting the jumper provided directly at the power
supply. Or you can enable the overclocking function by pressing the switch on the slot cover provided as
needed�
The overclocking key is connected to the power supply using the connector labeled accordingly.
When you switch on the overclocking function at the slot, a LED lights on the slot cover switch.
Important: Only press the “Overclocking Key” when the power supply is switched off!
Only connect the overclocking key, or the jumper provided, to the Overclocking Key connector on the power
supply! Do not connect any other device – such as a fan – to this connector!
To ensure trouble-free system operations, you should disable the overclocking key if you do not need this
function�

 

[BiggieShady]

Modular PCIe connections are numbered ... rails in the table are also numbered ... these numbers match.

 

[rtwjunkie]

Modular PCIe connections are numbered ... rails in the table are also numbered ... these numbers match.
View attachment 68835 View attachment 68836

That's pretty much the way I've always used multi-rail PSU's. The side panel has them numbered and it usually matches the connector listings, so I know if I need to use 2 rails for example to power a GPU.

 

[thebluebumblebee]

Modular PCIe connections are numbered ... rails in the table are also numbered ... these numbers match.
View attachment 68835 View attachment 68836

Really? So PCI-e connectors 1-4 line up with 12V1-4? So where do the P8/P4 and main 24 pin connectors get their power from? I'm not telling you that you are wrong, I'm just questioning your logic and pointing out the quandary of multi-rail PSU's.

 

[rtwjunkie]

Really? So PCI-e connectors 1-4 line up with 12V1-4? So where do the P8/P4 and main 24 pin connectors get their power from? I'm not telling you that you are wrong, I'm just questioning your logic and pointing out the quandary of multi-rail PSU's.

Usually it's not a big mystery to use multi-rail PSU's. This unit appears to be more confusing in its listings than others I have used without issue.

 

[Vayra86]

Really? So PCI-e connectors 1-4 line up with 12V1-4? So where do the P8/P4 and main 24 pin connectors get their power from? I'm not telling you that you are wrong, I'm just questioning your logic and pointing out the quandary of multi-rail PSU's.

Correct. P8/P4 is generally the cable you want to put on the 12V rail that you do NOT use for any other big component like a GPU. In the end, the cables are numbered but it means nothing, it's just an artificial limit from the manufacturers end, and a bit of quality of life added to the product. However, seeing as this is a high quality unit that can also 'merge' the rails into a single rail (see earlier post), I doubt it matters all that much.

Even within multi rail PSU's there can be big differences, the actual true multi rail PSU's are very rare.

 

[EarthDog]

I use the EVGA 1000w p2 it is silence even with fan spinning but most of the time the fan is off. It would only turn on when the Psu is at 50% load or it touches 50 celcius in temperature which for me never happen as I overkill it for my rig. I am a fan of having good Psu. If there is an EVGA Rma centre near you the 10 years warranty would be great!

Nice..a 1KW PSU for a system that wont break 200W. Wow.

 

[Vayra86]

I use the EVGA 1000w p2 it is silence even with fan spinning but most of the time the fan is off. It would only turn on when the Psu is at 50% load or it touches 50 celcius in temperature which for me never happen as I overkill it for my rig. I am a fan of having good Psu. If there is an EVGA Rma centre near you the 10 years warranty would be great!

Yeah, that's not very bright. You know the power efficiency curve is very bad at the lower end of the spectrum? You are wasting lots of energy there.

 

[R-T-B]

Yeah, that's not very bright. You know the power efficiency curve is very bad at the lower end of the spectrum? You are wasting lots of energy there.

I wouldn't say "lots" of energy, it's platinum rated and will still do quite well even on the low end. That said, there are cheaper ways to get a 200W Silent PSU.

Also, wow. $180 for a 750W PSU? I know these are solid units, but hell. You can have an EVGA that is just as good or better for $130 (after MIR) with a 10 year warranty. Damn.

The Corsair HXi has a fluid db fan as well and is a pretty decent unit (despite having a bad one just burn up on me, I still think they are pretty well made).

But a lot of his cost may have to do with locales. No idea what the upmark in Slovenia is.

 

[RejZoR]

I've used PSU calculators and did some watt-o-meter testing and it recommended me 650W units even for overclocked system. I've had 750W before and it was fine. On desktop, my system uses around 90-95W on the PSU plug, probably even less now with a better PSU.

As for efficiency, yes, below 25% it is worse, but with platinum units, it's still better than silver has at top efficiency!

 

[R-T-B]

I have to say despite any cost anaylsis, I'm liking what appears to be an integrated fan controller in that PSU. Cool!

 

[64K]

Using 200 watts on a 1,000 watt Platinum PSU drops the efficiency from 92% at half load to 90% at 20% load

https://en.wikipedia.org/wiki/80_Plus

Even if he were running his rig at full load 24/7 it wouldn't amount to much. If you do the math that 2% loss of efficiency would raise his electric bill by 35 cents a month if he's paying the national average here in the USA of 12 cents per kWh. Still that is an awful lot of money spent for such a large PSU for his rig.

 

[EarthDog]

Absolutely true 64K!

The point is the MUCH higher initial price versus other PSUs that were out which are just as good or better with a better warranty.

 

[cdawall]

Me personally? I wouldn't worry about it. If you trip the OCP then start looking into which rail is which. If it bothers you until the end of days break the powersupply open and start tracing circuits.

As for the EVGA 1000w guy...they make 200w power bricks and you can use a DC-DC board. There wont even be a fan in the powersupply setup.

 

[EarthDog]

If it bothers you until the end of days break the powersupply open and start tracing circuits.

Not something I recommend to anyone that is not experienced... it can kill you. Id sooner flip the thing to single rail mode (problem solved) or email/call the company and see what is what.

I will tell you I am not sold on the numbers corresponding with the rails though...

 

[RejZoR]

Modular PCIe connections are numbered ... rails in the table are also numbered ... these numbers match.
View attachment 68835 View attachment 68836

I'd say it's not that simple...

 

[newtekie1]

Yep, what @cdawall said. It doesn't really matter, it is all one big 12v rail anyway. If you trip the OCP, then move some stuff around, but I haven't really seen that happen on any decently designed PSUs. Usually, in a case like this unit, the PCI-E each get their own rail, the two rails that are rated higher also share the CPU and other 12v components.

There are not true multi-rail PSUs anymore. I think the last one I saw was the HX1000.

 

[rtwjunkie]

I think the Antec HCP is a true quad rail.

 

[RejZoR]

I can just flip it in single rail mode, but frankly, if I can set it up with OCP giving me additional protection, why not.

 

[EarthDog]

Yep, what @cdawall said. It doesn't really matter, it is all one big 12v rail anyway.

But we don't know that for sure. It is likely, but there are enough out there to make one wonder. Really though, all it takes is OCP on the rails not reaching the full output to make it a 'true' multi rail PSU

I can just flip it in single rail mode, but frankly, if I can set it up with OCP giving me additional protection, why not.

You still get OCP... its is not any more safe with multiple rails at this power level.