Question about +12V rails

[potsNpans]

My Antec EA-750 PSU I currently have lists its power output on the 12V rails, with 4 +12v rails each with a max load of 25A. I'm considering a new GPU, which requires a 42amp 12v rail and would like to know if my current PSU would suffice? The card I'm looking to run is a EVGA GTX 780 3GBhttp://www.newegg.com/Product/Product.aspx?Item=N82E16814130917. Would my current PSU be up to the task?

[Auger]

Potsnpans, if you look at the 5th picture in the link for that card, it shows the top view of the video card.  On the left you can see two black connectors with a total of 14 pins.  That is where you will plug in the supplementary power for the card.  Newegg's write up for your PSU show it has a PCI-Express Connector with 2 x 6-Pin, 2 x 6+2-Pin connectors.  You'll be fine.

[olds442]

He is asking about the amperage...
If you combine two of the rails you should be fine yes. 25+25=50A

[BaldEagl]

He is asking about the amperage...
If you combine two of the rails you should be fine yes. 25+25=50A

I wouldn't be so sure of that.  

Volts x Amps = Watts.  If he has 4 x 12V rails @ 25A ea. then his PSU should be rated at 1200 Watts at 100% efficiency.

Similarily, if it's rated at 750 W with four +12 volt rails equally rated then @ 100% efficiency each rail can only carry 15 amps; not enough to run the card unless he's somehow able to connect all four rails.

We know that no power supply runs at 100% efficiency and we're also not deducting wattage for the +5V circuits.

This is simple PSU marketing trickery.  They're probably rating the rails at max load which is not sustainable but may be available for micro seconds.  Reputable PSU maufacturer's don't resort to this and it's a good idea to check this when buying a PSU.

I'd warn you to use at your own risk.

[MrRiplEy[H]]

Single rail design PSUs are easyer to evaluate

[olds442]

I wouldn't be so sure of that.  

Volts x Amps = Watts.  If he has 4 x 12V rails @ 25A ea. then his PSU should be rated at 1200 Watts at 100% efficiency.

Similarily, if it's rated at 750 W with four +12 volt rails equally rated then @ 100% efficiency each rail can only carry 15 amps; not enough to run the card unless he's somehow able to connect all four rails.

We know that no power supply runs at 100% efficiency and we're also not deducting wattage for the +5V circuits.

This is simple PSU marketing trickery.  They're probably rating the rails at max load which is not sustainable but may be available for micro seconds.  Reputable PSU maufacturer's don't resort to this and it's a good idea to check this when buying a PSU.

I'd warn you to use at your own risk.

Most power draw is on the 12v rails anyways. He has an 850 watt PSU so at 50 amps on 12 volts thats 600 watts. Now what maters is the other stuff connected to the computer that draws on the 5v and 3.3v He has to look at and estimate how much he is drawing per rail before he can put two rails in parallel.

[BaldEagl]

Most power draw is on the 12v rails anyways. He has an 850 watt PSU so at 50 amps on 12 volts thats 600 watts. Now what maters is the other stuff connected to the computer that draws on the 5v and 3.3v He has to look at and estimate how much he is drawing per rail before he can put two rails in parallel.

He said it was 750 Watts.  If it's 80% efficient that's 600 Watts total for a maximum of 50 amps across all the 12V rails (53 amps @ 85% and 56 amps @ 90%).

Frankly I don't care what he does but if you're going to make these recommendations I hope you're prepared to replace the parts that fry when they do.

[Masherbrum]

He said it was 750 Watts.  If it's 80% efficient that's 600 Watts total for a maximum of 50 amps across all the 12V rails (53 amps @ 85% and 56 amps @ 90%).

Frankly I don't care what he does but if you're going to make these recommendations I hope you're prepared to replace the parts that fry when they do.

Correct.    Correct on both accounts.   

[olds442]

He said it was 750 Watts.  If it's 80% efficient that's 600 Watts total for a maximum of 50 amps across all the 12V rails (53 amps @ 85% and 56 amps @ 90%).

Frankly I don't care what he does but if you're going to make these recommendations I hope you're prepared to replace the parts that fry when they do.

First off. You have no idea what the rest of the power draw is on the system. 750 watts is good FOR ANY single graphic card system out there. Even some 2 way graphic cards.

[Skuzzy]

BaldEagle is quite right.  You also have to consider Antec does "marketing" numbers on the rails of their power supplies.  They do not provide a true rating based on actual usage.

I would avoid using Antec and get a better quality supply.

[potsNpans]

Thank you for your helpful input. I will be doing some more reading on power supplies units, and EVGA cards power draw.

[Bizman]

BaldEagle is quite right.  You also have to consider Antec does "marketing" numbers on the rails of their power supplies.  They do not provide a true rating based on actual usage.

I would avoid using Antec and get a better quality supply.

The Antec model in question is most probably made by Delta Electronics, just for the record. Delta seems to have a reasonably reputable name, but you never know what Antec has told them to build.

[Skuzzy]

The Antec model in question is most probably made by Delta Electronics, just for the record. Delta seems to have a reasonably reputable name, but you never know what Antec has told them to build.

There is a reason Seasonic stopped building many of Antec supplies.

[Bizman]

Skuzzy, are you reading my mind? Should I be worried about that? -Well, as long as you're working for HTC instead of NSA I suppose I'm safe.. 

[Brooke]

What are good PSU brands in addition to Seasonic, and what are some brands folks don't like?