PSU's---2 x 12v---The Dual Rail Myth

[RemusM]

[quote author=DOK]
[quote author=RemusM]
If you own a 2000 USD rig is more than a stupidity to buy & use a cheap PSU for it.
[/quote]
You are rite but people are still using cheap psu's in hi end rigs, Go Figure
[/quote]

Unfortunately that's true.
And I told them: "Don't cry if your PSU will explode, catch fire, and burn down the building".

 

[ex_forum_user_3]

Its so sad most of the time, they make a ? 2000 machine but the PSU may only cost like ? 30 tops.
But they don't realise that a ? 30 PSU can kill their ? 1970 machine just like that.

In my opinion people that don't know about PSU's should be forbidden to build a computer in total.

I have said this a billion times before, a PC starts with a good powersupply, forget that and your system will have troubles and blowups all the time.

 

[Aaron]

Well I tend to pick a PSU as the last choice. As you need to know you're power requirements before even the thought of what PSU to purchase. But the most important thing you need to chose when purchasing a PSU is the amperage on the +12v rail(s) [single rails preferred obviously]. There is also the factor of watts, it's just as important as amps. You could have 100A on the +12v rail, yet only have a total wattage rating of 500. So the PSU is only capable of delivering around 33A (assuming the other rails take 20% of the wattage requirement).

Getting the most amps with the most watts is the best way to go - but amps should always be thought of first.

 

[rhradacut]

I can say this, the first thing before anything else for my current rig is I bought my Corsair PSU +12V single rail.

 

[Hans]

Well, I caused quite some noise in here ... heh heh.

Did you see the TRIPPLE ... (no, no tripple rail, better ...) TRIPPLE FAN unit? I just love to make some NOISE!! :lol_anim:

 

[rhradacut]

To evacuate the smoke faster? :lol_anim:

 

[Del UK]

On a serious note:

Qtec power supplies, have caused many fires around the World.

At the very least you risk your computer.............

Think once, think twice, is the lure of Qtec worth your life?

This is my opinion and not the opinion of the following:-

MSI

MSI Forum

MSI forum users

 

[Hans]

On a serious note:

Qtec power supplies, have caused many fires around the World.

At the very least you risk your computer.............

Think once, think twice, is the lure of Qtec worth your life?

This is my opinion and not the opinion of the following:-

MSI

MSI Forum

MSI forum users

That is not entirely true. It IS the opinion of those running this forum.
Just go to Search, type "Q-Tec", select Hans as user to search for and see ...  :lol_anim:

 

[Del UK]

That is not entirely true. It IS the opinion of those running this forum.
Just go to Search, type "Q-Tec", select Hans as user to search for and see ...  :lol_anim:

But, may also be opinion of MSI Forum User Hans.......

 

[One-go]

funny, why i world  u want spend ur money and use somesing like Q-Tec?
would not even bother to look at anything like that.

my chose of PSUs:

Enermax Galaxy, or PC Power & Cooling (u cant beat this one : http://www.pcpower.com/power-supply/silencer-750-quad-crossfire.html) , or SliverStone, or OCZ (little bit expencive, but have 3 years warranty)

 

[flobelix]

Choose PC Power & Cooling, Silverstone (Olympia or Decathlon series), Corsair (VX or TX series) or Tagan (2-Force II series)! Those are single rail all others are split rail!
Split rail is (what this thread is all about) a gamble....

 

[One-go]

Choose PC Power & Cooling, Silverstone (Olympia or Decathlon series), Corsair (VX or TX series) or Tagan (2-Force II series)! Those are single rail all others are split rail!
Split rail is (what this thread is all about) a gamble....

its not realy gamble, its meter of reading inforamtion, provided by manafacturer, actualy reading between lines. and if information is purposly hided by manafacturer or seller, there no doubts its is crap PSU.

 

[flobelix]

Seems you didn't have a read here so I'm wondering your posting. Even if the manufacturer tells you about the specs of a split rail, it's still a split rail.
OCZ for example says your psu would have 4 20A rails which means 75A "combined". But it's a split rail so how can amps on splitted rails be combined? If too much power is drawn from one rail that's it, no matter if there are 3 or 5 others left still offering full 20A. So it's a gamble because you don't know if there is maybe too much load on one rail although you would have enough power in total...

A single rail offers all available +12v power on one rail so all +12v power is drawn from that rail and you can be sure there will be no problems as long as you have enough amps.
 

 

[One-go]

Seems you didn't have a read here so I'm wondering your posting. Even if the manufacturer tells you about the specs of a split rail, it's still a split rail.
OCZ for example says your psu would have 4 20A rails which means 75A "combined". But it's a split rail so how can amps on splitted rails be combined? If too much power is drawn from one rail that's it, no matter if there are 3 or 5 others left still offering full 20A. So it's a gamble because you don't know if there is maybe too much load on one rail although you would have enough power in total...

A single rail offers all available +12v power on one rail so all +12v power is drawn from that rail and you can be sure there will be no problems as long as you have enough amps.
? ?

actualy ON BOX state, Max Output Current for all 4 rails 66A, and i manual sed, its can be provided only for 60sec, so there is enouth information.? to have idea how much u can have on each rail, its simply get 80% out of Max. combined output, and divide on amount of rails.? that what aprox. u can get from each rail. to calculate aprox. Max. combined Currant output not difficult too, from max Power output PSU (for example my ) 1010W? deduct 25W (output from -12V&+5Vsb) 1010-25 = 985W, then deduct 175W (output from +3.3V&+5V) 985 - 175 = 810W, the divide by 12V 810 / 12? = 67.5A , bum for rough calculation not to bad, as long OCZ state 66A. then 80% out of 67.5 x 0.8 = 54A, split on 4 54 / 4 = 13.5 A that what u can expect form each rail of my PSU anytime at any moment. u not need to be Rocked scientist to calculate this. another thing, if u dont bother to learn, but in this case nothing i can do.
Its is true for unexpirenced user better use single rail PSU, at least they can see what is what, compere to dual or quad rail, but they , unexpirenced, anyway will go for cheap PSU with big Watts on box, they never consider PSU vital part of the computer, untill they RIG/system run into the trubble(overheating, low performance, or even damanging/killing parts of RIG/system), then they start cry and blaim manafacturer for bad quality and ect. ect. ect.

actualy, from ur post i can see u dont know how to calculate "combined" currant output.

about overlading one rail, if u building ur own RIG, for sure u know which hardware u use and u know how much roughly its requare Watt/Amps. and for sure u know to which rail u connect each hardware. example: again take for example my PSU and my RIG .on PSU state, +12V1 - CPU rail, +12V2 - pirmary Video adapter, +12V3 - peripherals, +12V4 - secendary Video adapter. rail N1 , my CPU , at stock speed, requare 125W. even if i push it hard , i would not be able overload this rail. rail N2 pirmary video adapter, according ATI on average its need 100w, OK my is O/Ced, well 120W, nop, not overloded. rail N3? peripherals, gosh u realy need try hard to overload this one,unelss of couse u manage connect cofe making mashin to ur RIG, or Microwave. Rail N4 practicly same with N2, exept its take nominal wattage, u cant Overcloak secendary video card in CrossFire, no meter how hard u try. he we go, load spread nicely over all 4 rails, non of them overloaded. to overload one rail and leave all other underloaded, u have to, have no ideas what u do whatsoever. in this case, there no point even try build ur own RIG, just pup up to nearest computer shop and ask specialist do it for u. its will save ur time, cash and headaches.

P.S. sorry for misstakes and bad spelling, english never was my strong side.

 

[flobelix]

Nice calculation....

1. Basically this is what OCZ states for GameXStream 1010W:

http://www.ocztechnology.com/products/power_management/ocz_gamexstream_power_supply_1010w

can't find 66A max output in there... BTW: 66A max output would also be ridiculous for a 1010w psu...

2. Obviously you didn't understand my point: If rails are really split they can't be combined as a rail from which is drawn too much power can't be compensated by another. That's the idea of splitting rails to dedicate a rail e.g. to the vgas.
The combined value you impressivly calculated is a theoretical value of total +12v power available on all rails. This on the other hand does not mean that a rail could compensate the lack of power on another rail.
With a psu as powerful as yours this won't have much effect because the rails are strong enough but for a psu from a lower price level this could be a crucial point.

 

[One-go]

Nice calculation....

1. Basically this is what OCZ states for GameXStream 1010W:

http://www.ocztechnology.com/products/power_management/ocz_gamexstream_power_supply_1010w

can't find 66A max output in there... BTW: 66A max output would also be ridiculous for a 1010w psu...

2. Obviously you didn't understand my point: If rails are really split they can't be combined as a rail from which is drawn too much power can't be compensated by another. That's the idea of splitting rails to dedicate a rail e.g. to the vgas.
The combined value you impressivly calculated is a theoretical value of total +12v power available on all rails. This on the other hand does not mean that a rail could compensate the lack of power on another rail.
With a psu as powerful as yours this won't have much effect because the rails are strong enough but for a psu from a lower price level this could be a crucial point.

that what u can see on BOX. anyway, actualy rails can compensate, if one or 2 rails underpowered? u can get some, not much, Amps to other rails. say in sutuacion if u use for rail N1 89W CPU and have not many hardrives and optical drives on N3, rails N2 and N4 can exide to 16A. That numbers 20A on each rail? its test values when all other rails set to 1A. 75A value come from when +3.3&+5 set to 1 A and +12 rails pushed to the limit.

 

[flobelix]

75A value come from when +3.3&+5 set to 1 A and +12 rails pushed to the limit.

That's peak not max! Max output is just maximum +12v. If OCZ just states peak values on their website and doesn't point that out then we got Q-Tec style.

The 75A on the sticker provided by me is for OCZ1010GXSSLI while your's is OCZ1010GXS. Maybe it's a different version for your local market. As the stickers are besides the combined +12v value absolutely identical it would be a bit odd if two calculation models are used for the same product.

 

[ex_forum_user_3]

To put it real simple:

Splitrail = Gamble

Singlerail = Exactly knowing what it can/will do

Fond of gambling? By all means do get a splitrail :lol_anim:

Can a splitrail do 66A on a single line? They state not, they say it can do only 20 or such, then it should shutdown.
Does it? Is it a splitrail at all? Many brands say they are splitrail but they are not.
But you don't know unless you open the PSU itself (void warranty) and follow all lines.

As said, if you like gambling, go splitrail :lol_anim:

 

[Aaron]

To put it real simple:

Splitrail = Gamble

Singlerail = Exactly knowing what it can/will do

Fond of gambling? By all means do get a splitrail :lol_anim:

Can a splitrail do 66A on a single line? They state not, they say it can do only 20 or such, then it should shutdown.
Does it? Is it a splitrail at all? Many brands say they are splitrail but they are not.
But you don't know unless you open the PSU itself (void warranty) and follow all lines.

As said, if you like gambling, go splitrail :lol_anim:

The Corsair HX620W was a great example of this. It said 3 x +12v rails rated at 18A on the box/website. Upon opening the PSU, I found that +12v led to a single point on the PSU. Therefore it wasn't split rail, but single.

actualy ON BOX state, Max Output Current for all 4 rails 66A, and i manual sed, its can be provided only for 60sec, so there is enouth information.  to have idea how much u can have on each rail, its simply get 80% out of Max. combined output, and divide on amount of rails.  that what aprox. u can get from each rail. to calculate aprox. Max. combined Currant output not difficult too, from max Power output PSU (for example my ) 1010W  deduct 25W (output from -12V&+5Vsb) 1010-25 = 985W, then deduct 175W (output from +3.3V&+5V) 985 - 175 = 810W, the divide by 12V 810 / 12  = 67.5A , bum for rough calculation not to bad, as long OCZ state 66A. then 80% out of 67.5 x 0.8 = 54A, split on 4 54 / 4 = 13.5 A that what u can expect form each rail of my PSU anytime at any moment. u not need to be Rocked scientist to calculate this. another thing, if u dont bother to learn, but in this case nothing i can do.
Its is true for unexpirenced user better use single rail PSU, at least they can see what is what, compere to dual or quad rail, but they , unexpirenced, anyway will go for cheap PSU with big Watts on box, they never consider PSU vital part of the computer, untill they RIG/system run into the trubble(overheating, low performance, or even damanging/killing parts of RIG/system), then they start cry and blaim manafacturer for bad quality and ect. ect. ect.

actualy, from ur post i can see u dont know how to calculate "combined" currant output.

about overlading one rail, if u building ur own RIG, for sure u know which hardware u use and u know how much roughly its requare Watt/Amps. and for sure u know to which rail u connect each hardware. example: again take for example my PSU and my RIG .on PSU state, +12V1 - CPU rail, +12V2 - pirmary Video adapter, +12V3 - peripherals, +12V4 - secendary Video adapter. rail N1 , my CPU , at stock speed, requare 125W. even if i push it hard , i would not be able overload this rail. rail N2 pirmary video adapter, according ATI on average its need 100w, OK my is O/Ced, well 120W, nop, not overloded. rail N3  peripherals, gosh u realy need try hard to overload this one,unelss of couse u manage connect cofe making mashin to ur RIG, or Microwave. Rail N4 practicly same with N2, exept its take nominal wattage, u cant Overcloak secendary video card in CrossFire, no meter how hard u try. he we go, load spread nicely over all 4 rails, non of them overloaded. to overload one rail and leave all other underloaded, u have to, have no ideas what u do whatsoever. in this case, there no point even try build ur own RIG, just pup up to nearest computer shop and ask specialist do it for u. its will save ur time, cash and headaches.

P.S. sorry for misstakes and bad spelling, english never was my strong side.

You can't calculate the combined output of a split rail PSU. The rails are split, not combined. If you could combine them, they'd call them combined railed PSUs. They are called split rails, because they are split.

75A is (like Flobelix said) a joke for a 1010W PSU... My Corsair TX750W can do 60A @ +12v. At peak I would assume it's about 70A and because it's single rail; I know it will do the 60A stated on the box.

 

[One-go]

My Corsair TX750W can do 60A @ +12v.

realy, can do 60A. let me see, what is formula for WATTS, ahhh W = A x V. well if ur PSU be able do 60 A , its mean its would draw 720W. max output on ur PSU 750W, r u planning supply +3.3V, +5V, -12V and +5Vsb with only 30W? good luck with that.

split rails , in reality not completely split, they attached to same power source. all true, if u do not use one rail, u cant transfer all Amps to other, but this allow other rails perform better. all 4 rails together can draw more power, than PSU can produce its self. technicly each rail have capacity of 240W, but in reality they cant draw so much, its would exide Max.output of PSU. 1010 - 25 ( to-12V and +5Vsb) , then u have to allocate some power to +3.3V and +5V (not need go for Max. values 100W would be enouth), 985W -100 = 885W left, its alot less than all 4 rails can draw 240 x 4 = 960W , i dont know why im argue with u, go back to school and refresh Physics course. to make it little bit simpler, in overal, if u drop out one rail, u lose Amps: lets go with max Currant, 66A for 4 rails, 60A will for 3 rails(when u use only 3 rails), 40A for 2 rails(when u use only 2 rails) , 20A for single(when u use 1 rail , technicly inposible to achive.)

its easy and cheaper produce multi-rail PSU than single rail, also, if u dont know single rail PSU more efficent than multi-rail PSU, so there no surprise 850W single rail PSU would achive same numbers (Amps) as 1kW multi-rail PSU


P.S.
"The 75A on the sticker provided by me is for OCZ1010GXSSLI while your's is OCZ1010GXS. Maybe it's a different version for your local market. As the stickers are besides the combined +12v value absolutely identical it would be a bit odd if two calculation models are used for the same product."

look at sticker again, by 1010W? u will see small print, what its say?

"That's peak not max! Max output is just maximum +12v. If OCZ just states peak values on their website and doesn't point that out then we got Q-Tec style."

all companies do that, corsair too, i would hardly believe they achive 60A on 750W units with proparly loaded +3.3V&+5V
to stop this argue, why do u simply go and ask Corsair? how much load was on +3.3V&+5V , when they achive 60A.( would not surprise if they say 9W , which is 1A for each)

and last one, good or not, but by some reason i cant see Corsair TX750W certified to run RIG with 2x HD 2900XT/XTX or 2x HD 3870X2, when my "s***y" unit does, and yes its was tested , i had 2 x HD2900XT my self , and sold it on ebay. if ur PSU (Corsair one) realy can provide 60A, that would be more than enouth to supply them. (ATI recomend 52A continuos for CrossFire with HD2900/HD3870X2)
good luck in future