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Is this a good PSU for this system?

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March 24, 2011 5:17:35 AM

Hi, first post on TH. I have just finished a build and have some doubts of whether or not the PSU is good enough for this system. Here are the specs:

Asus Rampage III Formula (I have plugged in the Asus "EZ Plug")
Intel i7 950 D0 Revision, NOT OVERCLOCKED
TWO ATi Radeon HD 6970s in CrossfireX, NO OVERCLOCK
Noctua NH-D14 with included fans, connected directly to PSU
OCZ Vertex 2 60GB
Kingston HyperX 12GB Kit (3x4GB Modules) 1600MHz DDR3, NO OVERCLOCK/VOLT
Western Digital Caviar Black 1TB
1 SATA DVD-RW drive
Sentey GS-6400B (my case, included because it has a card reader and 6 (probably cheap) fans connected by molex connector)

I have up to 5 USB devices in at once. My PSU is the Siverstone OP-800, an 800W PSU with 60A on 12V rail. Is that good enough for my system? Some of the PSU calculators (newegg, eXtreme) say no. Thanks a ton!

More about : good psu system

March 24, 2011 9:39:39 AM

According to http://www.thermaltake.outervision.com/Power

you are about to hit the threshold cause with the things you listed you are at about 726W at 90% peak. So you might want to reconsider changing to a better one...
March 24, 2011 10:04:39 AM

Yeah, that's what worries me. Perhaps if keep the case fans off and/or unplug the DVD drive, I can safely use this PSU?

EDIT: Also, is Silverstone OP800 a bad brand of PSU, because the PSU was fairly cheap on Newegg and it did have pretty good user reviews?
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a c 91 ) Power supply
March 24, 2011 10:14:37 AM

www.antec.outervision.com/PSUEngineer

You are close to using 100% of your PSU.. If you consider overclocking your CPU then you will be risking your rig for power actually.. Best to get a slightly beefier PSU..

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a b ) Power supply
March 24, 2011 10:18:02 AM
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fans or dvd drive dont use much power. Silverstone is considered a good brand. I would have thought 2 x 6970's would be ok on 800w take a look at toms most recent build http://www.tomshardware.com/reviews/intel-sandy-bridge-... only 587W with 2 overclocked 6950's and overclocked cpu. http://www.legitreviews.com/article/1488/18/ this show close to 600w for 2 6970's. those are at the wall watts so its more like less than 500w assuming 85% efficiency.
March 24, 2011 10:37:05 AM

Emperus said:
www.antec.outervision.com/PSUEngineer

You are close to using 100% of your PSU.. If you consider overclocking your CPU then you will be risking your rig for power actually.. Best to get a slightly beefier PSU..


I realize that I am cutting it a bit close, but since I don't plan to OC any of the hardware at any point in this PC's life, you guys think I can manage with this PSU or will it still give me problems under load?

iam2thecrowe said:
fans or dvd drive dont use much power. Silverstone is considered a good brand. I would have thought 2 x 6970's would be ok on 800w take a look at toms most recent build http://www.tomshardware.com/reviews/intel-sandy-bridge-... only 587W with 2 overclocked 6950's and overclocked cpu. http://www.legitreviews.com/article/1488/18/ this show close to 600w for 2 6970's. those are at the wall watts so its more like less than 500w assuming 85% efficiency.


That evidence seems to conflict with the messages that I am getting from the PSU calculators. Honestly, I'm not sure what to make of this. Either the PSU calculators are overestimating, or I am misinterpreting those power usage results. I currently feel it's more likely the latter.
a c 105 ) Power supply
March 24, 2011 11:42:03 AM

PSU Calculators tend to overestimate. I believe they use worst-case scenarios. OTOH, what someone has actually measured with test equipment will be valid; but note any differences between the tested system and yours.
Here's an idea...get yourself a Kill-a-Watt meter. Pull out one of your GPUs and measure what your system is using under full load. Then decide if it is safe to add the second card, or if you need to upgrade your PSU first. Heck, you may even decide that your gaming performance with just one card is sufficient, in which case you can sell the other one.
March 24, 2011 12:01:41 PM

Psu calculators DO underestimate. http://www.anandtech.com/bench/Product/298 as you see during Furmark the system uses 600w total. Imo that psu should be powerful enough. And if you still wanna be sure, get a Kill-a-Watt meter or like i did - a Zalman ZM-MFC3 fan controller, it has a power load meter.
March 24, 2011 5:23:21 PM

Thanks for both replies.

I actually have load tested it. While I haven't done any marathon load sessions, I have run Crysis (30m), Prime95 (Blend 3h), Unigine Heaven (3h), and Furmark (only a few min, chickened out after seeing GPU temps). In each case, the system was stable. However, I don't know if that means I can assume the parts are correctly powered. The kill-a-watt sounds like a great idea.
a c 91 ) Power supply
March 24, 2011 5:38:10 PM

If you are not gonna overclock then that PSU is enough.. But, you may eventually require to overclock as your processor at its stock speed might start limiting your video cards..
March 24, 2011 6:26:27 PM

Emperus said:
If you are not gonna overclock then that PSU is enough.. But, you may eventually require to overclock as your processor at its stock speed might start limiting your video cards..


Would an i7-950 really limit 6970CFX, or are you referring to future cards?
March 24, 2011 9:43:10 PM

Did you just say an i7 950 would bottleneck a gpu ?! o.O No way a 950 or any i7 would limit any released gpu, mabie after 2-3 years if technologies advance alot but no way right now. :D  And if an i7 950 would bottleneck a gpu then what are you supposed to get ? o.O an i7 990x ? :D  :D 
March 25, 2011 7:17:58 PM

oc_mania said:
Did you just say an i7 950 would bottleneck a gpu ?! o.O No way a 950 or any i7 would limit any released gpu, mabie after 2-3 years if technologies advance alot but no way right now. :D  And if an i7 950 would bottleneck a gpu then what are you supposed to get ? o.O an i7 990x ? :D  :D 


Heh, good point. So I guess I'll consider the setup I have to be fine, as long as I avoid OC (not something I intended to do anyway).
March 29, 2011 8:07:10 AM

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