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PSU Size required?

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September 3, 2012 10:02:33 PM

Dear Users,

I'm in the process of parting out my first gaming build, and I ran into a little snag. On my first post for the build, I got some pretty solid feedback that the Corsair HX 850w PSU would be more than enough to run my computer. However, when I started playing around with throwing an extra GPU into SLI, I got a little doubtful about an 850w/70A PSU being enough.
This is my build:

Corsair 650D
Mushkin chronos 240 GB SSD
WD Caviar Black 1TB
Intel i7 3770k OC to 4.8GHz (I realize that this may not be possible on air, but I'll use this as an upper limit for the draw on the PSU)
Coolermaster 7PC812 fan
Asus P8Z77 Pro/Thunderbolt motherboard
Corsair Vengeance 2x8GB ram (May upgrade to 4x8GB if needed eventually... highly doubt it though)
Evga GTX 670

Not sure if the following will make much difference to a PSU or not,
1x Blueray drive
1x DVD burner
1x DasKeyboard pro S
1x Razer Black Mamba
1x Raid card (Possibly)
1x Sound card (Possibly)

I'm sure that an 850w is more than enough to run the above, but when I put an extra GTX 670 into SLI, and maybe even OC them, will it still be enough? The Thermaltake PSU calculator says to keep an extra 25-30% wattage due to capacitor aging if you plan on keeping the PSU for more than a year. Any thoughts on this as well?

Thanks a lot,

John

More about : psu size required

a b ) Power supply
September 3, 2012 10:49:49 PM

850w from a good brand like XFX or Seasonic is good enough.

2x 8GBs Corsair is also not a route I would go. Not sure what you intend to do with this computer but it can probably be done with 2x 4GBs of 1333/1600 if there are 2x GTX 670s in it. Crucial and Kingston are more reliable brands as well.
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a c 243 ) Power supply
September 3, 2012 11:02:29 PM

JohnGalt1 said:

I'm sure that an 850w is more than enough to run the above, but when I put an extra GTX 670 into SLI, and maybe even OC them, will it still be enough? The Thermaltake PSU calculator says to keep an extra 25-30% wattage due to capacitor aging if you plan on keeping the PSU for more than a year. Any thoughts on this as well?

850w is more than enough for SLI with your specs ( will make all the guys who believe you need twice as much wattage as you will use happy )
With a high quality power supply in a well cooled modern system capacitor aging is something you might have to think about after the 7 year warranty runs out
September 4, 2012 4:30:41 AM

Quote:
850w is more than enough for SLI with your specs ( will make all the guys who believe you need twice as much wattage as you will use happy )
With a high quality power supply in a well cooled modern system capacitor aging is something you might have to think about after the 7 year warranty runs out - delluser1


This is great to hear, thanks. I really couldn't figure out for the life of me why you would lose 30% of your power to capacitor aging... it seemed a bit much to me. Especially over only a year of use.

Quote:
2x 8GBs Corsair is also not a route I would go. Not sure what you intend to do with this computer but it can probably be done with 2x 4GBs of 1333/1600 if there are 2x GTX 670s in it. Crucial and Kingston are more reliable brands as well.- Raiddinn


I'm mostly going to use the computer for gaming. I'd like to try my hand at botting in D3, see how that goes. I went for 16GB of 1600 MHz ram just because the price difference really isn't that much. Would you go for 8GB's purely because this is quite a bit over kill?


Quote:
850W will be more than enough for 2x 670s + the other things that you mentioned. 750W will probably be sufficent too, but I'd go 850W to be sure.
- nafoni


This is good to hear. Do you guys think the Corsair HX 850 would be enough for a third OC Gtx 670, or would that be stretching it a little bit? I'm leaning towards this being just a little bit too much. Plus it'd probably add a *** ton of extra heat to the case, not to mention reducing the airflow to the GPU's.

The answers you guys have provided have been great, and I'd love to hear another round of responses.

John
a c 111 ) Power supply
September 4, 2012 4:31:22 AM



Quote:
Our test system is based on a power hungry Core i7 965 / X58 system. This setup is overclocked to 3.75 GHz.

Measured power consumption one card

System in IDLE = 140 W
System Wattage with GPU in FULL Stress = 279 W
Difference (GPU load) = 139 W
Add average IDLE wattage ~10 W
Subjective obtained GPU power consumption = ~ 149 Watts

Measured power consumption two cards in SLI x2

System in IDLE = 160W
System Wattage with GPUs in FULL Stress = 433W
Difference (GPU load) = 273W
Add average IDLE wattage ~20W
Subjective obtained GPU power consumption = ~ 293 Watts

Measured power consumption three cards in SLI x3

System in IDLE = 170W
System Wattage with GPUs in FULL Stress = 583W
Difference (GPU load) = 403W
Add average IDLE wattage ~30W
Subjective obtained GPU power consumption = ~ 433 Watts


You can run 4 GTX 670's off of an 850W.
a c 158 ) Power supply
September 4, 2012 12:10:27 PM

Nice Amuffin!
a b ) Power supply
September 4, 2012 1:41:07 PM

I would add that a good brand/model 850w will be able to do 4x 670s. Not just any old 850w. It will also definitely not allow for any OCing of pretty much anything.

Maxing those cards in gaming, assuming you could do it, would put you at like 90% of stated wattage which is strain I would generally not suggest most people commonly place on their PSUs. A 950 would be a safer choice, either that or stick with 3-way SLI.

RAM - Games can really only use 2GBs for the most part anyway, so 16 GBs would really just allow you to run the OS, browsers, and like 6 games at once.

I normally suggest 2x 4GBs because that leaves you with 2 for the OS, 2 for a game, and the other 4 will generally cover whatever else you want to have open like 100 browser tabs and iTunes or whatever. It is pretty hard to use up 8GBs on a gaming PC.

High end audio/video programs that are 64 bit can use much larger amounts of RAM, but I haven't heard of any 64 bit games. They are all made 32 bit for the maximum backwards compatibility (IE so they can run on XP). As such they are pretty much limited to 2GBs of RAM each.
September 5, 2012 3:11:50 AM

Thanks a lot guys, your answers have been absolutely perfect. I've decided that the Hx 850 should be more than enough. The most I'll ever have sucking on that thing will most likely be an OC 3770k, and 2x Gtx 670. Chances are I'll never get a third one in there, (and definitely not a fourth :p  That was just for curiosity's sake)

Thanks again,

John
!