# PSU with switch between single and multi rail



## spectatorx (Jan 21, 2019)

Recently i spotted that psu to be on nice deal and most probably will buy it:
https://www.corsair.com/eu/en/Power/Plug-Type/hxi-series-2017-config/p/CP-9020138-EU
But one thing makes me curious: it has a switch to set operational mode between single and multi rail. If i understand correctly this is something what requires proper layout on psu's pcb so it can be just single or just multi or am i wrong? Can be one psu both and have option to switch between both modes?


----------



## EarthDog (Jan 21, 2019)

One PSU can be both, yes. It likely just bypasses whatever power limit they have on the rails when single is enabled. There really isn't a reason to change it off single rail.


----------



## DeathtoGnomes (Jan 21, 2019)

I'd check the CPU against the rating list (in my signature)

HXi series is top tier, so should work as you expect


----------



## EarthDog (Jan 21, 2019)

HXi is a high quality unit... no need.


----------



## spectatorx (Jan 21, 2019)

Thanks for letting me know about this list, seems like change of purchase decision from seasonic focus plus (tier 2 on that list) to this one (tier1) is good, especially as price difference is fairly small.


----------



## EarthDog (Jan 21, 2019)

LOL, the difference will not be noticeable except on testing equipment. If the Focus is cheaper, get it. 

That said, you can also easily rock at 650W PSU with that setup and overclock both as well as have headroom... can save you even more money.


----------



## spectatorx (Jan 21, 2019)

EarthDog said:


> LOL, the difference will not be noticeable except on testing equipment. If the Focus is cheaper, get it.
> 
> That said, you can also easily rock at 650W PSU with that setup and overclock both as well as have headroom... can save you even more money.


850 will give me more headroom which will be possibly needed as i plan to purchase top navi gpu once it will be released. Focus is cheaper by just about 10% so...


----------



## EarthDog (Jan 21, 2019)

650W will still allow overclocking Navi and that AMD CPU and leave headroom. If you are worried, go 750W. 850W is just wasting money on ambient cooled single card/single CPU setups. 

10% is 10%. No point in paying more.


----------



## Vya Domus (Jan 21, 2019)

The main reason there are multi rail PSU nowadays is because there are some restrictions with regards to how much current can be passed through a single conductor. So manufactures got around that by increasing the number of rails.

There is really no advantage or disadvantage. If anything, single rail is better because sometimes GPUs can draw so much power it can trigger OCP protections ,even though electrically everything is fine.


----------



## EarthDog (Jan 21, 2019)

Vya Domus said:


> The main reason there are multi rail PSU nowadays is because there are some restrictions with regards to how much current can be passed through a single conductor. So manufactures got around that by increasing the number of rails.


Nowadays, it is not as common to find TRUE multi-rail PSUs... There are MONSTER single rail PSUs out there.


----------



## spectatorx (Jan 21, 2019)

Now decision is settled: shop changed price of that corsair psu and it is 10% cheaper than seasonic focus plus 650W.


----------



## Bill_Bright (Jan 21, 2019)

EarthDog said:


> There really isn't a reason to change it off single rail.


^^^This^^^



Vya Domus said:


> The main reason there are multi rail PSU nowadays is because there are some restrictions with regards to how much current can be passed through a single conductor. So manufactures got around that by increasing the number of rails.


Sorry, but that is not, and never was true. That is not how electricity works. The current through any circuit is determined by the demand the load puts on the supply. If the demand on the 12V circuit is 300W, the PSU will deliver 12 volts  at 25 amps (12V x 25A = 300W). It does not matter if the supply is a 500W supply or a 1000W supply. 

So it is then up to the motherboard designer to ensure any demands through any motherboard circuit do not exceed the ATX standards. Note for graphics cards, the PCIe standard allows for a maximum of 75W through the PCIe slot. But we all know many cards demand much more than that so they get their additional power via separate power cables directly from the PSU. 

It is not about restrictions on current that can be passed through a conductor. Nor is it about manufacturers getting around those restrictions (except graphics card makers). In fact, multiple rails imposes restrictions! Why? If you have  a supply that is rated for 500W at 12V, and that 12V is split between two rails, then the maximum the supply can deliver on any one rail is 250W! What if your monster graphics card needs 300W. You will be out of luck because in effect, you just have two small 250W PSUs when what you need is a 300+ watt supply. 

There are more sophisticated multi-rail supplies that can automatically redistribute some of the available power from one rail to another rail. But they must always leave some in reserve on all rails. And note those supplies are also more expensive and more complex with more components that might fail. 

So in multi-rail supplies, there will always be restrictions preventing delivery of the full capability of the supply. 

In a single rail, full power is always available.

Multiple rail PSUs for computers really are just a marketing gimmick. In other electronics, where power "isolation" is desired for "fault tolerance" scenarios (where you don't want a failure in one connected device to take down another) multi-rail supplies may be desired. In a data center, for example, you might have an equipment rack populated with 10 server computers, all powered from a single power supply. You don't want a fault in the power circuit for one computer to take out the remaining nine servers. So that PSU would be multi-rail with each rail being isolated from the other. 

In a single PC with a multi-rail PSU, if you lose the 12V to your motherboard, does it really matter if you still got 12V going to the graphics card? No. To your fans or drives? No.



Vya Domus said:


> There is really no advantage or disadvantage.


Ummm, sorry, but also not true. As I noted above, a major disadvantage is some of the PSU's capability must be reserved for each rail - even if that rail is unused. Multi-rail PSUs are more complex, thus they have more potential failure points, and they cost more. On a single rail system, all the power is available. They use a simpler design for more reliability and lower costs.


----------



## EarthDog (Jan 21, 2019)

spectatorx said:


> Now decision is settled: shop changed price of that corsair psu and it is 10% cheaper than seasonic focus plus 650W.


How much is the 650W version of the Corsair?


----------



## MrGenius (Jan 21, 2019)

More PSU power...more bettah! I fully disagree with the whole trying to buy the least powerful/least expensive option you can find that will suffice methodology. I've killed enough PSUs to know the folly in that.


----------



## Vya Domus (Jan 21, 2019)

Bill_Bright said:


> Sorry, but that is not, and never was true.



I know, it never is with you. Spare me the wall of text.


----------



## spectatorx (Jan 21, 2019)

EarthDog said:


> How much is the 650W version of the Corsair?


Local stores use PLN currency. Seasonic focus plus 650 is around 500pln, mentioned corsair hx 850W is at the moment 450pln, this particular store doesn't have hx650 but hx750 and this one is 600pln. All of these 80+ platinum certification.


----------



## eidairaman1 (Jan 21, 2019)

spectatorx said:


> Local stores use PLN currency. Seasonic focus plus 650 is around 500pln, mentioned corsair hx 850W is at the moment 450pln, this particular store doesn't have hx650 but hx750 and this one is 600pln. All of these 80+ platinum certification.



http://www.realhardtechx.com/index_archivos/Page447.htm

http://www.orionpsudb.com/corsair

Channel Well Technology is the OEM, 750hxi is a custom pcb, so it's brand specific pcb, you wont find this in antec, coolermaster etc.


----------



## Bill_Bright (Jan 21, 2019)

Vya Domus said:


> I know, it never is with you. Spare me the wall of text.


Then do your homework first, research and learn the facts before posting. Bing Google is your friend. It really is that simple.





MrGenius said:


> More PSU...more bettah!


 Same with this. A little homework would reveal the truth. Power supplies tend to be most efficient when run with 50 - 60% loads most of the time. If the supply is way oversized, they could be running at 20 or 30% most of the time and wasting energy - even with a quality 80 PLUS supply.

You don't want to max out the supply all the time, and some headroom is wise for future upgrades (and quieter operation). But more PSU is NOT necessarily "more bettah".


MrGenius said:


> I fully disagree with the whole trying to buy the least powerful/least expensive option you can find that will suffice.


I fully agree with this. I don't know who suggested otherwise - certainly no one in this thread. I have always recommended getting a "quality" supply from a quality maker since EVERYTHING inside the computer case depends on good, clean stable power. But users don't need to buy Platinum or Titanium certified or the most expensive, biggest supply they can find either. I would not suggest Platinum unless it was on sale at a "too good to pass up" price. I generally recommend at least Bronze and preferably Gold certified - with the total understanding 80 PLUS certification does NOT imply quality or reliability.


----------



## EarthDog (Jan 21, 2019)

Bill_Bright said:


> Power supplies tend to be most efficient when run with 50 - 60% loads most of the time. I


True, but the difference is literally 1% or so between 50 and 75%, nearly negligible. I prefer to run my PSUs around the 75% mark (this is stress testing fully loaded GPU and CPU - not a gaming load). I have a few more ducketts in my pocket left and no hardware is worse for the wear. 



Bill_Bright said:


> I don't know who suggested otherwise


I recommended a 650W unit... but of high quality... A 650W unit is plenty for Navi (assuming 300W here) and this CPU both overclocked and with plenty of headroom. That said, of these two options, I DID in fact suggest the least powerful and least expensive option.....but only because I know those options are both top notch PSUs and will EASILY handle his current and proposed system.


----------



## 95Viper (Jan 21, 2019)

Back on topic, please.
If you want to discuss personal business, take it to PMs.
Quit the personal bickering.

Thank You.


----------



## Bill_Bright (Jan 21, 2019)

EarthDog said:


> I prefer to run my PSUs around the 75% mark


Actually, that's pretty much where I size them too!


----------



## spectatorx (Jan 21, 2019)

Bill_Bright said:


> ... I would not suggest Platinum unless it was on sale at a "too good to pass up" price. I generally recommend at least Bronze and preferably Gold certified - with the total understanding 80 PLUS certification does NOT imply quality or reliability.



Since shop changed price of that hx850 this is the cheapest platinum psu i've seen since i'm watching psus prices which is about 6 months.


----------



## eidairaman1 (Jan 21, 2019)

spectatorx said:


> Since shop changed price of that hx850 this is the cheapest platinum psu i've seen since i'm watching psus prices which is about 6 months.



If you can get yourself a gold base get yourself a gold base


----------



## Bill_Bright (Jan 21, 2019)

eidairaman1 said:


> If you can get yourself a gold base get yourself a gold base


I agree. Unless that HX850 Platinum is priced super low (in the "Gold" range), you don't need to spend the money for the Platinum logo.


----------



## MrGenius (Jan 21, 2019)

Bill_Bright said:


> Same with this. A little homework would reveal the truth. Power supplies tend to be most efficient when run with 50 - 60% loads most of the time. If the supply is way oversized, they could be running at 20 or 30% most of the time and wasting energy - even with a quality 80 PLUS supply.
> 
> You don't want to max out the supply all the time, and some headroom is wise for future upgrades (and quieter operation). But more PSU is NOT necessarily "more bettah".


1. The higher the efficiency of the PSU = the less any of that is relevant.
2. If you're going for the least powerful unit that will suffice for your needs, you're probably going to be running it at higher than 50-60% loads frequently. And you'll be losing a bit of efficiency then too. Factoring in that sweet spot for efficiency generally means a significantly more powerful PSU than one might theoretically be able to get away with(like basically 2x as much power as you "need").
3. Not that efficiency should be a primary concern when purchasing a PSU. What you want is enough power to handle the loads you'll be giving it without stressing components to a premature death(as in be able to handle 50-60% or more for the long run). And/or a PSU with high enough quality components to handle being stressed to near max output capacity for extended periods without resulting in premature death(if you insist on going the "barely enough" route).
4. The price of PSUs seems to be coming down lately. Making you far better off to get a spendy one that has excellent efficiency and a very high power output capacity with a 10 year warranty. Buy 1 and done!!!


----------



## spectatorx (Jan 21, 2019)

Sidenote observation: i see silver rating is not common, in stores are available up to few models, even less than platinum. I wonder why.


----------



## EarthDog (Jan 21, 2019)

MrGenius said:


> 1. The higher the efficiency of the PSU = the less any of that is relevant.
> 2. If you're going for the least powerful unit that will suffice for your needs, you're probably going to be running it at higher than 50-60% loads frequently. And you'll be losing a bit of efficiency then too. Factoring in that sweet spot for efficiency generally means a significantly more powerful PSU than one might theoretically be able to get away with(like basically 2x as much power as you "need").
> 3. Not that efficiency should be a primary concern when purchasing a PSU. What you want is enough power to handle the loads you'll be giving it without stressing components to a premature death(as in be able to handle 50-60% or more for the long run). And/or a PSU with high enough quality components to handle being stressed to near max output capacity for extended periods without resulting in premature death(if you insist on going the "barely enough" route).
> 4. The price of PSUs seems to be coming down lately. Making you far better off to get a spendy one that has excellent efficiency and a very high power output capacity with a 10 year warranty. Buy 1 and done!!!


1. Why?
2. You will be... and yep, ~1% difference give or take.
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story4&reid=392
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story4&reid=553

from 50% to 100% is 3% difference in the first place. So it has to be less than that. 80 Plus spec Bronze, silver, gold, all 3% max.

Its not worth it to spend that much more cash (to almost 2x your PSU wattage) for that small % increase, agreed!! 

One should expect that a quality unit should be able to output its label rating(s) over the course of the warrantied period. Ideally we do not want to run it like that for more than one reason (noise to name another). 

If it came down to it, my advice for the OP is to get whichever one is cheaper. Since that 850W is cheaper than even a 650W unit (which would be plenty), it couldn't even hurt the wallet this time around. DO IT. 



spectatorx said:


> Sidenote observation: i see silver rating is not common, in stores are available up to few models, even less than platinum. I wonder why.


That is a good question. There are several around, but it doesn't seem as common as bronze or gold... especially these days.


----------



## DeathtoGnomes (Jan 22, 2019)

I took the Silver rating as marketing hype. There is not enough wiggle room between Bronze and Gold given their price differences to add another tier of PSU efficiency rating with single digit percentage performance for less than $5?$10?.  It would have cost more to replace the stickers on a Bronze PSU and call it Silver.


----------



## spectatorx (Jan 24, 2019)

Purchased hx850 and all i can say it is pure quality, really amazing psu.


----------



## EarthDog (Jan 24, 2019)

spectatorx said:


> all i can say it is pure quality, really amazing psu


Because turning on your PC and running tells you that... 

Regardless, glad it works!


----------



## spectatorx (Jan 24, 2019)

EarthDog said:


> Because turning on your PC and running tells you that...
> 
> Regardless, glad it works!


I mean psu as a whole, packaging and bundled items too. Not just that it is running and running well.


----------



## EarthDog (Jan 24, 2019)

Packaging and accessories don't make it run well either.

You don't have the testing equipment. All you know is that it is working and your system is running fine. A potato can do that for a while. Now, I get it, we know its a quality PSU because people who know how to and have the proper equipment to test it showed us this. Again, just because you turned it on and it is working doesn't give you the wherewithal to claim its quality. 

You will now be returned to your non hair splitting production.


----------

