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AX1200 - overkill for this build?

J

Joe Fission

Limp Gawd
Joined
Jan 15, 2006
Messages
167
I'm building a new rig and need some advice on what PSU to use to power the whole thing. This will be the most powerful rig I've built for myself so far, so some of this is new territory which is part of the reason I'm having so much trouble deciding.

Here's the specs:

- AMD Phenom II x6 1090T (will be OC'ed... aiming for 4GHz for now)
- ASUS Crosshair IV Formula
- either 8GB or 16GB of DDR3
- a couple ODDs, 3 or 4 HDDs, and maybe a couple of SSDs
- 2x 5870 cards in Crossfire... the choices so far are Powercolor PCS+ 5870 and the Sapphire Vapor-X 5870

Will an AX1200 be extreme overkill for this system? I'm looking for something that's quiet, runs cool, quiet, is efficient, and quiet. Oh, and quiet. (Ya I know OC'ing and quiet normally aren't used in the same sentence... but I'll see what I can do.) I read that PSUs are at their most efficient when they are at about 40% to 60% power consumption. I don't actually have any of the components for this system yet but from the estimates I've seen on the net and from results of other PSU calcs, I have estimates of anywhere from 500W to 800W power consumption for these components (not sure if those numbers factored in OC'ing)... which just happens to be in the 40% to 60% range. It also gives me quite a bit of headroom for upgrading later. I also like the fact that apparently the AX1200 supplies quite clean, solid power.

Am I just deluding myself and are the estimates way out to lunch? Would I be better off with a PSU a little less powerful (AX850 perhaps?) even if I were to do something really wacky like add a 3rd 5870? Or if I were to swap out the 5870s for NVidia 4xx series cards in SLI or something?

Any help and insight is appreciated.

JF
 
using the extreme psu calculator v 2.5, using your specs and overclock, with a 1.4v vcore, it came up with 728 watts. so yes, 1200watts is overkill, depending on what you think you will be upgrading to in the next 2 or 3 years. the 850w should be o.k., but personally i would go with a 900w or a 1kw just to leave a little headroom for future upgrades.

http://extreme.outervision.com/index.jsp
 
I'd get a 750W PSU for that. There's no reason to get anything more unless you find a really good deal. The AX1200 has much more power than you need and costs far more than you need to spend.
 
Well, assuming 728 watts is a semi-accurate number, it's even been posted here in these forums that a PSU lasts longest, runs the coolest, and runs the quietest typically around 40% to 60% power consumption (I can't find the exact post at the moment... I just read it today...found it in a Google search), then it would seem almost a better idea to go with a 1200 watt PSU, no? After all, 728 watts is like 61% usage on a 1200 watt, it's also about 86% usage of an 850 watt, and 73% of a 1000 watt PSU. The way I figure it, if I were to get a lower power PSU, not only would I be taxing it more, but it would build up more heat... more heat means the fan on it has to run faster and louder which is not what I'm looking for. Or is there a flaw with this line of thinking?
 
728W is not a semi-accurate number for that system. I'd guess maybe 500-600W under gaming load.
 
OK... I think I'm convinced. Just found a few other snippets on the intartubes regarding systems with similar specs as the one I'm building that have power consumption numbers that jive more with the 500 to 600 watt estimate.

So, I've set my sights on something a bit less monstrous but still quiet and efficient... the AX850.
 
Yes. A 1kW PSU would be too much. Unless you're stress-testing everything at once, even 850W is overkill.
 
You wont need as high as you think. When gaming, your CPU wont have 6 cores loaded, so power draw will be less. Then perhaps when you are video encoding, your video cards will be idling. I plan on getting 2 high video cards soon, and all I got was an AX750.
 
well unless youre an uber multi tasker, you wont be running your system at full bore all the time. And most likely when you are running it at full bore youll have something producing sound to cover up the sound of the PSU.
 
Nothing wrong with buying a PSU thats too big for your system. Not running it up to its max load will make it last longer and having the extra potential is nice for future upgrades such as next gen video cards that require massive amounts of power.

And the cables on the AX850 are kind of funky because of the proprietary connection and two cables on a single plug for the video cards at least. (14 pin plug).

I prefer the AX1200s cables that are totally different with a standard 8 pin plug for each cable.
 
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