Which PSU for crossfiring 280x's?

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jkteddy77

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Okay, These are on sale NOW and are quite trusted brands. I'm no expert at this, which is why I ask this. I need this to last for a good 4-5 years (or as long as possible, they each have warranties) and not outdate with whatever new parts I put into the build over time. This isn't just a "Get the Corsair" question, I want to know if the seasonic thats $40 less will be almost as good as the corsair and be able to handle the stress of being maxed out. Can the seasonic even support crossfire?
Corsair HX850
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139011
or
Seasonic M12ll 850AM
http://www.newegg.com/Product/Product.aspx?Item=N82E16817151108

If I can't use the seasonic, I will most likely get Corsair, for its Really cheap and I trust them better than the competition. And lastly, Is the 850w enough for 2 280x's? The 12v rail has 840w on it. I really don't feel like paying $200 for a quality 1000w.

P.S. Also still undecided on which 280x I should buy yet. I've always had my eyes on the Sapphire Vapor-x, but is it the coolest running 280x? I don't want toxic versions, just the slight OC custom cooler cards.
 
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Kingbob

Kingbob

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The difference between 80 plus gold and 80 plus bronze is actually pretty big. If you were to get an 80 plus platinum, you could get away with a 700w PSU and it could x-fire 2, 290x's. With bronze, you would need about 850w so the seasonic would be fine for what you need.
 
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J

jkteddy77

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You sure though? the seasonic says that it can run SLI and not Crossfire, so . . . . plus, the seasonic only has 4 6+2 pins. Won't that limit me now or in the future? every 280x is either 6+8 or 8+8.
 
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jkteddy77

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It seems every OC'd + Special cooling 280xs requires 2x8pins, so I guess I have to pay for the Corsair. I won't settle for Burning up 280x's since I don't want to pay extra for exterior cooling, and 7970/280x can get BURNING hot.

Also, do you know why every 280x recommends 750w for single and 1000w for crossfire? seems like overkill to me. Should I trust those numbers? cards are still so new.
 
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Kingbob

Kingbob

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It is overkill, you do not need 1000w for two cards. Like I said before, I know someone that runs 2 x 7970's with a 700w Platinum PSU.

Think about it this way, each 280x will take, at most, about 300w. And the rest of the system will be around 250w. This adds up to 850w total, and this is on the highest side.
 
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J

jkteddy77

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Thanks guys, I think I'll go for the Corsair since the 280x's I want are 2x8pins. I thought those power numbers were bull . . . I think the Gold rating will be a plus too, since this monsterous build needs to last me quite a while. I had to return a crappy 835w Raidmax a friend recommended. Of course it was DOA and far too weak. 700w on the 12v rail . . . Newegg gouged me with a $12 restock fee and a $15 shipping cost . . . $50 back on a $95 product, so hope this sucker is worth it.
 
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P

Prostar Computer

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just a note: you should go at least a little "overboard" with how much wattage the PSU can supply versus how much is required, because over longer periods of time those PSUs just can't quite put out the wattage they started with. They come down a little, believe it or not. sounds like you might have found a good solution though.
 
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jkteddy77

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You personally believe a High quality gold Corsair HX850 with 840w on its 12v rail will be enough?
 
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Vic 40

Vic 40

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I read this and i couldn't believe it.
Since when does efficiency has something to do with what a psu can deliver? It is about what a psu pulls out of the wall.

If that 700watt platinum psu can xfire 2 R290X's a good bronze unit should be able to do the same.

If a psu states that it can deliver 750watt,it should be able to do that and i'm not speeking about peak power.
The difference is in what the psu gets out of the wall,a bronze pulls let's say 850watt out of the wall when a gold psu will pull 800watt out of the wall to deliver the 750watt (just examples).That's the difference and then there is your electricity bill.

I know that there are cheapass psu's that say they can deliver 750watt but burn when you try and max them out,but this seasonic isn't one off those.
And off course a gold labeled psu has probably better internal components,but the bronze unit should be doing just fine as well.

Each of those two psu's will be able to power 2 R280X's.

It also has to do with your other components.Do you have a powerhungry cpu for instance,like an amd 8core or a i7 3960K or do you have a i5 2500K,3570K.There's a big difference there in power usage.
In the next review you can see the difference in power usage between those cpu's,
http://uk.hardware.info/reviews/2575/25/intel-core-i7-3960x--3930k-sandy-bridge-e-reviewed-energy-consumption-idle--cinebench-115

About what a system with one R9280X will use during a game,in this instance metro,and this is with a i7 3960K (not overclockt!),
http://uk.hardware.info/reviews/4892/7/amd-radeon-r9-280x--r9-270x-from-asus-and-msi-review-r9-in-practice-cooling-noise-production-and-energy-consumption
this is measured at the wall,efficiency stil needs to be applied->328:100x85*=~280watt that the system really uses.

*from what i gather they use a bronze rated unit-> Cooler Master Real Power M850.

If you have the money i'd say buy the corsair,but when not the seasonic should be fine.There probably is a good difference between the warranty periods in favour off the corsair.



 
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jkteddy77

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Very well put, I know the efficiency only saves you a good couple bucks a year, just the parts in it last longer. I need this thing to last 4-5-6 years or so. I decided against the Seasonic, becasue it simply doesn't have enough pins to crossfire 2 280x's that I want. Stock ones, yeah, but the overclocked variants are each 8+8 pin. I bought the corsair since updating this, and it was even cheaper than almost every other 850w at the moment, so I'm satisfied with buying a nice componenet without totally breaking the bank. I'm using an 8350 which takes 125w. I have a decently good Mobo that most likely uses 70w. I will use 1 DVD-RWdrive, and 1 HDD, so I expect the absolute max of this system to reach around 740w stock. I left a little overhead for PSU/PC life, and incase I use a slight OC on the 8350. I think I should be good. Thanks for the input!

 
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Vic 40

Vic 40

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Even the seasonic has 4x6+2 pins which is the same as 4x8pins,6+2=8. ;)
Regardless you made a good choice,so have fun with it.
 
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