# GTX 275 in SLI power requirements?



## leopardforest

I am going to get  a GTX 275 and I would like to run SLI in a couple months. I plan on getting a Corsair 850, would that be enough power?

the rest:
i7
room for 3 hdd


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## Bodaggit23

The GTX 275 isn't on this list yet, but I think you could squeak by with that psu,
but you may want to consider a 1000Watt instead.

http://www.slizone.com/object/slizone_build_psu.html


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## leopardforest

Bodaggit23 said:


> The GTX 275 isn't on this list yet, but I think you could squeak by with that psu,
> but you may want to consider a 1000Watt instead.
> 
> http://www.slizone.com/object/slizone_build_psu.html



I cant really speak from experience, but that just seems like overkill (referring to that link) compared to what people are using?


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## Bodaggit23

leopardforest said:


> I cant really speak from experience, but that just seems like overkill (referring to that link) compared to what people are using?


Well I thought Nvidia would know better than you or I what to use.
Like I said, you could probably get by with the 850. It's a great psu.

Consider a Single GTX 275 requires:


> Minimum of a 550 Watt power supply
> (Minimum recommended power supply with +12 Volt current rating of 40 Amps.)


I can't find an SLI "Minimum Requirement" for that card, which is what you're looking for,
so I linked the "Recommended Specs".

Running SLI is overkill in my opinion. I think it's unnecessary. 
You won't get twice the frame rate, so why spend twice the money?

You can game just fine with a single card, but if you're going for benchmarks then knock yourself out.


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## kennebell347

is there any single card that can completely max crysis out? i mean completely max it out?


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## dsolash

kennebell347 said:


> is there any single card that can completely max crysis out? i mean completely max it out?


??? wrong thread dude, but the GTX 295 can somewhat do it. 

And 850w will be more than enough to run those 2 cars in sli. You would have no problems what so ever.


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## Bodaggit23

dsolash said:


> the GTX 295 can somewhat do it.



Somewhat? I can play Crysis maxxed out on my GTX 260 at 30-40 fps,
so I'm sure the 295 can more than "somewhat" handle the task.

Crysis Recommended System Requirement:


> GPU - NVIDIA GeForce 8800 GTS/640 or similar



Also, the GTX 295 is not considered a single card, it has two gpu's.


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## dsolash

Bodaggit23 said:


> Somewhat? I can play Crysis maxxed out on my GTX 260 at 30-40 fps,
> so I'm sure the 295 can more than "somewhat" handle the task.
> 
> Crysis Recommended System Requirement:
> 
> 
> Also, the GTX 295 is not considered a single card, it has two gpu's.



But it is a single card so . Its a single card with dual Gpus. And i cant max out crysis even with my 4870x2 so thats why i stated that the GTX 295 can somewhat do it.


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## Bodaggit23

dsolash said:


> i cant max out crysis even with my 4870x2 so thats why i stated that the GTX 295 can somewhat do it.


Well I can, and that was my point, so nVidia ftw. :good:


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## CardboardSword

Bodaggit23 said:


> Well I can, and that was my point, so nVidia ftw. :good:



Not to nit-pick, but doesn't Crysis have a rather large nVidia bias? either way, if there is a game that the 295 can't devour, I'd like to see it.


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## mimic58

dsolash said:


> ??? wrong thread dude, but the GTX 295 can somewhat do it.
> 
> And 850w will be more than enough to run those 2 cars in sli. You would have no problems what so ever.



Er note quite,,,,  I just bought a second GTX275 hooked them up in sli on a 850w supply, All Was going great while i gamed of the hard disk , But then i put in Grid (which required the DVD rom) 

Needless to say i am now in need of a new damn psu 60 quid down the toilet it just damn killed it id had those cards in there about 30 mins  when they say you need 40amps on the rail they mean it trust me


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## ganzey

mimic58 said:


> Er note quite,,,,  I just bought a second GTX275 hooked them up in sli on a 850w supply, All Was going great while i gamed of the hard disk , But then i put in Grid (which required the DVD rom)
> 
> Needless to say i am now in need of a new damn psu 60 quid down the toilet it just damn killed it id had those cards in there about 30 mins  when they say you need 40amps on the rail they mean it trust me



dude that sucks. what brand of power supply was it?


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## mimic58

ganzey said:


> dude that sucks. what brand of power supply was it?



it was a W-win power EA4G-850 it had 20 amps per 12v rail 4 rails so i used two rails per card with the molex links their should of been 40 amps per card available but it didnt leave enough for the cpu , hdd memory etc

so far the only psu iv been able to find that looks like it can do it is this one 
http://www.antec.com/Believe_it/product1.php?id=MTc1Nw== 
But i dont know if the pci express power leads are off seperate 12v rails if i were to connect both cards to any one rail , its gunner kill it , What id really like is a psu with a single 12v rail raited at 100amps but i cant seem to find one anyware


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## ganzey

ouch, it was an offbrand so what can you expect.. but a single rail is better than one. a corsair 850 would be enough, since it has 70 amps on the +12v


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## mimic58

you reacon 70 is enough ?? the manual says 40 amps , and isnt clear if its per card or for the system aswell, I want to be able to run raid in the future and also have enough for the 965 quad


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## mimic58

ganzey said:


> ouch, it was an offbrand so what can you expect.. but a single rail is better than one. a corsair 850 would be enough, since it has 70 amps on the +12v



you think 70 is enough to handle the 4-6 drive raid + 965 quad ?? , The 275 manual states 40amps per card , and isnt really clear if its just for the card or for everything?


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## ganzey

mimic58 said:


> you think 70 is enough to handle the 4-6 drive raid + 965 quad ?? , The 275 manual states 40amps per card , and isnt really clear if its just for the card or for everything?



that means 40 amps is reccomended for the entire system, including the card. the card itself only uses around 15-22 amps. so a 70 would be enough. but only a good brand, like corsair, pc power and cooling, seasonic, silverstone, ocz.


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## mimic58

ganzey said:


> that means 40 amps is reccomended for the entire system, including the card. the card itself only uses around 15-22 amps. so a 70 would be enough. but only a good brand, like corsair, pc power and cooling, seasonic, silverstone, ocz.



how about this fellow ???
http://www.scan.co.uk/Products/1000...d-PCI-E-6pin-ATX-12V-22-and-EPS-12V-Std-80plu


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## ganzey

mimic58 said:


> how about this fellow ???
> http://www.scan.co.uk/Products/1000...d-PCI-E-6pin-ATX-12V-22-and-EPS-12V-Std-80plu



oh yea, thats more than enough. and a dang good price too


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## mimic58

ganzey said:


> oh yea, thats more than enough. and a dang good price too



Iv just found this http://www.hardwarecanucks.com/foru...0-nvidia-geforce-gtx-275-896mb-review-20.html

They measured the consumption using an inline meter , for some reason the 275 pulls more juice than most 

Watts / volts = amps 345 watts Devided by 12 = 28.8 amps! 

What the hell was i thinking buying two of these I had no idea what i was letting myself in for 
so now im needing dam near 60 amps just to run the cards 

what about the Cpu how much will a crosshair 2 , With an overclocked 965 quad core pull???


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## ganzey

mimic58 said:


> Iv just found this http://www.hardwarecanucks.com/foru...0-nvidia-geforce-gtx-275-896mb-review-20.html
> 
> They measured the consumption using an inline meter , for some reason the 275 pulls more juice than most
> 
> Watts / volts = amps 345 watts Devided by 12 = 28.8 amps!
> 
> What the hell was i thinking buying two of these I had no idea what i was letting myself in for
> so now im needing dam near 60 amps just to run the cards
> 
> what about the Cpu how much will a crosshair 2 , With an overclocked 965 quad core pull???



that power usage is for the entire system . so i think a 965 OC would take around 12-13 amps UNDER LOAD.


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## mimic58

ganzey said:


> that power usage is for the entire system . so i think a 965 OC would take around 12-13 amps UNDER LOAD.



Ah yes i see , i just looked at the 345 watts an thought Sh*T but i see now its only adding a hundred or so watts 

Sweet So that Beefcake they have on Scan website should easily be able to handle the two cards cpu m/b and the 4 way raid i was planning this is excellent news , Just wish i didnt have to go 3 days on this stock pc till new psu arrives , No games ARggg


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## jevery

Here's what I'm running with a Corsair 850HX, a pair of 4870s, a Q9650 (OC'd), 7 case fans, a 4 drive RAID, 2 DVD burners, a floppy drive, and a couple of cold cathodes.

I ran this setup successfully for over a year with a 4 rail 700 W Silverstone PSU. though, one day my RAID went down and I determined that I had overloaded a rail.  I'll be sticking with single rail PSUs from now on.  I think the 700 was marginal for everything that I eventually stuffed in the case.  Give yourself some room to grow and get the 850, or the 1000 and you should be good for the next build too.


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## Computer_Freak

kennebell347 said:


> is there any single card that can completely max crysis out? i mean completely max it out?



im running Crysis with a GTX295 @ 

1440 x 900, 
Ultra High settings (did the tweak that unlocks Ultra High for XP) 
4 x AA, 
16 x AF, 
shaders etc (in windows) set to highest quality

i get an average of 40fps...

the game is highly playable

but sometimes i get some lag and my frames drop


My card needs a recomended 650W PSU. Im running a E6400 OCed to 3.0GHz, GTX295, 2HDD, DVD writer, 8 fans, with a 750W corsair... Im sure i can maybe push 2 x GTX295 on my system (that will be seriously pushing it though)

Remember, nvidia recomends more than needed, that so people dont mess anything up. There was a guy here running a full system, with 2 8800GTS 512 on a 520W Corsair...

Trust me, a 850W (especially since its single rail) is plenty



mimic58 said:


> They measured the consumption using an inline meter , for some reason the 275 pulls more juice than most
> 
> Watts / volts = amps 345 watts Devided by 12 = 28.8 amps!



thats the power consuption of the whole system under load.

so you will be fine with a 850W PSU. Hell a 750W will even suffice


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## Okedokey

To the OP, please post the model of PSU you intend to buy prior to buying.

The two cards in SLI with standard clocks will draw no more than 440W.  That is 36A.  Just for the cards.

If you plan to overclock them or run them above 25oC ambient you risk drawing more current than that.

A TX750W Corsair has 60A on a single 12V rail.  This is sufficient for that system.  Anything less though is risking it.

http://www.newegg.com/product/product.aspx?item=n82e16817139006


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## NCspecV81

any reputable 750w psu will work for sli 275's. The corsair 850 would be overkill imho. However, it's always nice to have a little extra psu than needed.


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## The Chad

Found on Club 3D's info page for the GTX275:



> • Minimum 550Watt or greater system power supply (with a minimum 12V current rating of 40A)
> 
> • 800Watt or greater power supply for SLI™



http://www.club-3d.com/products/products_ending_page_7_with_id.cfm?product_id=131


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## Okedokey

Wattage doesn't mean a great deal.  There are plenty of higher wattage garbage units out there.


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## Christian Darrall

i'm sure if you buy a 1000w power supply it will have enough juice to run SLI and all the extra you may want to add in the future,

i cute have a nice SLI compatible PSU for under £100.00


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## mimic58

bigfellla said:


> Wattage doesn't mean a great deal.  There are plenty of higher wattage garbage units out there.



yeh i totally agree with this guy , iv looked at stacks of powersupplys since my 800 blew up , And 80% of them have multiple rails at arround 20 amps regardless of wattage the thing you want to be looking at is the 12v rail 

I'v opted to go for a single rail 80 amp and im confident i will now have enough juice to run the two cards mb and raid without any risk of overloading one of the rails

The other problem with multiple rail is you have no easy way of identifying which connectors are on which rails you could easy put to much onto one rail and not get the ballancing right


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## Computer_Freak

The Chad said:


> • Minimum 550Watt or greater system power supply (with a minimum 12V current rating of 40A)
> 
> • 800Watt or greater power supply for SLI™



see, that just proves that nVidia overcompensates, and takes into consideration bad quality PSU's.

a full GTX275 rig uses about 380W on load...

thats nearly 200 less than recommended...

800W is overkill, but nice to have, for future expansion, and so that the PSU doesnt run at max all the time.


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## mimic58

Computer_Freak said:


> see, that just proves that nVidia overcompensates, and takes into consideration bad quality PSU's.
> 
> a full GTX275 rig uses about 380W on load...
> 
> thats nearly 200 less than recommended...
> 
> 800W is overkill, but nice to have, for future expansion, and so that the PSU doesnt run at max all the time.



As already said wattage is not the issue its avialable current on the 12v rails and ability to distrubute the load


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## Okedokey

Look it comes back to quality and the PSU's ability to provide stable 12V current without overheating etc. etc.

nVidia requires a 550W PSU with 40A on it.  Well fine, however most people new to the mainstream PC PSU market make 1 or more of the following mistakes:


they believe that a PSU claiming to have multiple rails will.  Almost all of these PSUs actually only split the ONE 12V rail into several via voltage divders (electronics) rather than seperate physical windings on a transformer.
Wattage is important - its not directly important - amperage is (on the 12V rail)
add up the total 12V rail manufacturer stated amperage as a total avialble current on the 12V rail.  You cannot do this UNLESS it has EPS12 certification.

Here is an example of where wattage alone is very misleading:

550W Antec - 19A on the 12V rail available (ATX design limitations / no EPS)
550W Corsair - 41A on the 12V rail available (EPS)

Same wattage, different amperage.  Only one PSU (the Corsair) is able to run this setup.  So in this example you can see that there is absolutely no comparison that can be made between the PSUs.  More importantly there is no assessment that can be made based on the 550W minimum criteria alone.  Wattage means little.

Finally, don't purchase a PSU with 'just enough' power for your current system.  You may decide in 2 months to want watercooling or lights, or to overclock etc etc.  Go for a PSU with around 60A for expansion ability.  The HXCorsair is only $130 with a 7 year warranty, 90% efficiency (find that elsewhere), 60A on the 12V rail. http://www.newegg.com/Product/Product.aspx?Item=N82E16817139010&Tpk=corsair 750Hx

Perfect buy in this situation i reckon.


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## Computer_Freak

mimic58 said:


> As already said wattage is not the issue its avialable current on the 12v rails and ability to distrubute the load



thats why i said they overcompensate for bad PSU's

as Bigfella pointed out, it might have the same wattage, but much less current can be delivered. Thast what i meant they were overcompensating for

It is mostly the amps that is important, but the watts on the 12v rail usually depicts what the amps will be...


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## mimic58

Computer_Freak said:


> thats why i said they overcompensate for bad PSU's
> 
> as Bigfella pointed out, it might have the same wattage, but much less current can be delivered. Thast what i meant they were overcompensating for
> 
> It is mostly the amps that is important, but the watts on the 12v rail usually depicts what the amps will be...



Yeh i think your right , Their trying to cover themselfs for cheap hardware and rightfully so,  I used a cheap 800w supply and it didnt last 5 minutes


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## meticadpa

You can easily run SLi GTX 275s on a 750W power supply of decent quality.

You could probably use something like the Antec TruePower New 650W, but your power supply's life and efficiency may be lower than usual, as a result of the high load percentage.



Computer_Freak said:


> thats why i said they overcompensate for bad PSU's
> 
> as Bigfella pointed out, it might have the same wattage, but much less current can be delivered. Thast what i meant they were overcompensating for
> 
> It is mostly the amps that is important,* but the watts on the 12v rail usually depicts what the amps will be...*



Wattage ALWAYS = Amperage * Voltage. So if you've got 50A on the 12V rail, you do 50 * 12, to get 600W.

For multi-rail power supplies, you don't just add the rails together, but usually there's something that says "Don't get 12V load exceed 500W" for example, so you'd divide the figure that it states (in this case, 500W) by 12.


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## mimic58

meticadpa said:


> You can easily run SLi GTX 275s on a 750W power supply of decent quality.
> 
> You could probably use something like the Antec TruePower New 650W, but your power supply's life and efficiency may be lower than usual, as a result of the high load percentage.
> 
> 
> 
> Wattage ALWAYS = Amperage * Voltage. So if you've got 50A on the 12V rail, you do 50 * 12, to get 600W.
> 
> For multi-rail power supplies, you don't just add the rails together, but usually there's something that says "Don't get 12V load exceed 500W" for example, so you'd divide the figure that it states (in this case, 500W) by 12.



Yes but at what duty cycle can it maintain that current???
And how is your very basic ohms law calc factoring the diversity of the system and how the current is split, Your wattage may equate to 50amps but it maybe split over 5 rails at 10amps a rail with a duty cycle arround 80% meaning it can only deliver this full current for short periods (peak power)
Now you have a situation where any one rail cannot provide enough current to run the item so the rails have to be parralleled up together, Now because it is dam near imposible on most cheap supplys to actualy see which power connectors are connected to which rails , how can you garantee you have not connected a device to one single rail instead of say two 

You cant apply the Watts devided by volts = amps calculation here it just wont work unless its a Single rail supply and the duty cycle is 100%, |There is also the question of efficeincy , The ohms law calculation you have applied assumes a 100% efficiency in the power supply mean it converts 100% of the watts to amps, NO psu can ever offer this some watts are always lost to heat
on avarage expect about 90% efficiency at best


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## Okedokey

mimic, ill agree meticadpa is possibly using Year 10 physics as gospel, however what you are referring to relates to ATX design standard PSUs without EPS12.  In this case, meticadpa is right, the Antec true power has EPS12 certification so it can supply the nominal rail amperage as a total.


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## mimic58

bigfellla said:


> mimic, ill agree meticadpa is using Year 10 physics as gospel, however what you are referring to relates to ATX design standard PSUs without EPS12.  In this case, meticadpa is right, the Antec true power has EPS12 certification so it can supply the nominal rail amperage as a total.



what is the difference ?? The only referencess i can seem to find to EPS12 simply regard to the type of connectors and say nothing about duty cycle rail layout or deisgn differences from atx.. Obviously you know something i dont , Any chance you could explain? 


""pure guess, I'm assuming it allows it to channel all of its current to one output if needed?""


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## Okedokey

mimic58 said:


> what is the difference ?? The only referencess i can seem to find to EPS12 simply regard to the type of connectors and say nothing about duty cycle rail layout or deisgn differences from atx.. Obviously you know something i dont , Any chance you could explain?
> 
> 
> ""pure guess, I'm assuming it allows it to channel all of its current to one output if needed?""



Have you read it?   Pure guess, I bet you haven't.

 The latest EPS standard refers to:

* Removal to references to common and split 12V planes (ie you can add the 12V rails)
* Added cross loading plots (i.e you can add the 12V rails)
* Increase 12V rail currents (over and above 240VAC safety limits on ATX PSUs)

btw, efficiency issues will simply mean it will draw more amps from the wall to deliver the intended power - it doesn't work how you have described, and duty cycle is expressed practically in MTBF ratings, at least 40oC.  So really, with a 7 year warranty, who gives a shit.

*edit* oo i can hear google being hit hard now


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## Okedokey

congrats on the 1000 post freak!!!


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## mimic58

bigfellla said:


> Have you read it?   Pure guess, I bet you haven't.
> 
> The latest EPS standard refers to:
> 
> * Removal to references to common and split 12V planes (ie you can add the 12V rails)
> * Added cross loading plots (i.e you can add the 12V rails)
> * Increase 12V rail currents (over and above 240VAC safety limits on ATX PSUs)
> 
> btw, efficiency issues will simply mean it will draw more amps from the wall to deliver the intended power - it doesn't work how you have described, and duty cycle is expressed practically in MTBF ratings, at least 40oC.  So really, with a 7 year warranty, who gives a shit.
> 
> *edit* oo i can hear google being hit hard now



thats interesting, I know conventional switch mode power supplys do exactly the same thing and always have done.... But normaly they are limited by the raiting of their internal transistors like you cant pull 50 amps through a 25 amp transistor so regardless of the current at the wall socket, it cant allow more than its raiting without blowing up.. Sureley if your correct this would mean that the current flow on and EPS12 supply is not limited at all an can deliver what ever you have at the socket, But i cant see this being the case, It still has to switch the mode from AC to DC and smooth and regulate it thus it has to use components and these would have current limits.... these components would also still generate stacks of heat (hence the need for 3 Fans!) meaning your efficiency is not 100%

So unless your telling the components inside an EPS12 supply are superconductive , and can allow unlimited amounts of amps without generating any heat, They Cannot allow unlimited current and your supply is still going to blow up if you pull to much current


edit (" Belches loudly and fetches another bacon sandwich")


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## Okedokey

no one said anything about unlimited.  EPS12 PSUs basically allows you to overcome the dedicated to CPU 12V+1 rail as in standard ATX designs.  EPS allows for cross over between rails, which are not true multirails btw .  If a Corsair PSU can deliver 60A (720W) before shutdown, at 80% efficiency, it will draw 864W from the wall at max.


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## mimic58

yep agreed... most power supply raitings are given on there consumption not on what they actualy output..

but you have still not explained how you can exceed the current limit on the 12v side an eps12 powersupply without blowing up its internals..

Edit: AHHH i see now your explanation makes sence , It has the internal ability to bridge rails, So if you exceed the raiting of one rail it just pulls it from another one instead

Now this time what you say is perfectly sound

So the conclusion is that eps12 is as good as a Single rail, But is still limited by its total wattage thanks for taking the time to explain


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## Okedokey

mimic58 said:


> i see now your explanation makes sence , It has the internal ability to bridge rails, So if you exceed the raiting of one rail it just pulls it from another one instead



all consumer grade PC PSUs are single rail. electronically voltage split rails are not true multirails - as windings on a transformer are.  they are simply marketing bollocks,  but you get the concept finally.

mate, my text communication may have flavour, but i always appreciate the conversation with ya


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## mimic58

bigfellla said:


> all consumer grade PC PSUs are single rail. electronically voltage split rails are not true multirails - as windings on a transformer are.  they are simply marketing bollocks,  but you get the concept finally.
> 
> mate, my text communication may have flavour, but i always appreciate the conversation with ya



but to clarify this feature is only in these new eps12 supplys , if you try and pull to much from one rail on a normal atx supply it goes bang right??

likewise , It goods to get real information not forum myths


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## Okedokey

it can.  most reputable psu makers are single rail these days.  but with 1000W, you don't have to worry ever


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## mimic58

bigfellla said:


> it can.  most reputable psu makers are single rail these days.  but with 1000W, you don't have to worry ever



Good, Cus i really dont want to have another go, 
(Bang.... Stink.... No Games.... )


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## Okedokey

peace bro


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## mimic58

bigfellla said:


> peace bro



I hate to be a pain in the aris, But i have another question...

I just disected the 800w supply that blew up on me, And found that all of the 12v posative wires and all of the negative went to the same points on the PCB they were not split into 4 at all, Now on the outside of the box it says 4 12v outputs at 20amp, So im taking this to mean it should be combined at 80 amps and it wont matter what 12v wire you take it from cus they come from the same place on the board, I couldnt of been pulling over 80 amps based on whats been said about the consumption of my cards

So heres the question... Why did it go Bang?


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## mimic58

New Power supply turned up today , Installed it Bench tested my cards at full load..... No problems :good: didnt even crack a sweat


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## ganzey

^^nice


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