PSU for a GTX 690 advice needed plez

[Guest]

Hello people,

I would like some advice on a PSU for my new build.
First thing I'm wondering is, would 750w be enough for it with room to OC a little, or would I need 850w just to be sure???
Also I'm over budget so I need to shave a few quid off some parts to get back within it. So should I go for the top-end PSU and cut back on another parts or would one of the cheaper PSU's be ok.
I've been looking at PSU's that have good reviews and I've found these but I would like some extra opinions on them please.

System:
i5 3570k (Mild overclock)
ASUS z77 Sabertooth
8GB vengeance 1600
ASUS GTX 690 4GB
1x SSD and 3x HDD

PSU's Within budget:
XFX Core Edition ProSeries 750W 80+ Bronze - http://www.dabs.com/products/xfx-750w-80--bronze-certified-single-rail-75R8.html?q=XFX%20750w&src=16
XFX Core Edition ProSeries 850w 80+ Bronze - http://www.dabs.com/products/xfx-850w-proseries-80--bronze-core-edition-full-wired-psu-8B0G.html?q=XFX%20850w&src=16

Slightly over:
XFX ProSeries XXX Edition Semi Modular 850w 80+ Silver - http://www.dabs.com/products/xfx-850w-xxx-edition-single-rail-semi-modular-psu-7TD1.html?q=XFX%20850w&src=16
Antec 900W High Current Gamer 80+ Bronze - http://www.dabs.com/products/antec-900w-high-current-gamer-80plus-bronze-psu-7N3F.html?refs=50882&src=3

Over budget:
Seasonic X-850 850W Modular 80+ Gold - http://www.scan.co.uk/products/850w-seasonic-x-series-ss-850km-modular-80-plus-gold-eps-12v-quiet-fan-atx-psu

Any suggestions or advice would be brilliant.
Thanks

 

[rolli59]

The 750 will do it. Typically 690 calls for 650watt PSU in a system.

 

[manofchalk]

I bet you could getaway with using a 550W on that system, 750W is enough for two 690's.

 

[Guest]

I bet you could getaway with using a 550W on that system, 750W is enough for two 690's.

Really! Everything I've read so far says 650w minimum??

 

[rolli59]

650 is correct but based on generic cheap PSU's. High quality 550watt would run that system no problem. Max total system load under 500watts http://www.anandtech.com/show/5805/nvidia-geforce-gtx-690-review-ultra-expensive-ultra-rare-ultra-fast/16

 

[ko888]

For a system using a single GeForce GTX 690 graphics card NVIDIA specifies a minimum of a 650 Watt or greater power supply that has a combined +12 Volt continuous current rating of 46 Amps or greater and that has at least two 8-pin PCI Express supplementary power connectors.

Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Total Combined Continuous Power/Current Available on the +12V Rail(s) @ 50°C ambient temperature, is the most important factor.

 

[manofchalk]

This would have been the 550W PSU I would tell you to get.
http://www.newegg.com/Product/Product.aspx?Item=N82E16817207013&Tpk=XFX%20550W

You can see that it is low of the above figure by 2 amps, but remember that the Nvidia statement is probably based off the worst case scenario.
Such as an overclocked AMD chip (so ~150W draw), overclocked 690 (350W according to Toms), throw in another 30W for the mobo/RAM/anything else on the 12v. You have ~530W on the 12v rail (and 12V x 46A = 552W, pretty close) , so add another 100W for good measure and round it you have Nvidia's recommended wattage of 650W.
But if your on an Intel system, less power draw (-50W) and the misc category isn't really going to be drawing 30W (-15W), minus Nvidia's safe measures (-120W) and you got ~500W draw with everything under full load (which isn't a likely scenario). So on a 550W PSU (that can put out ~550W on the 12v) you have ~50W headroom to spare.

Of course given the non-exact nature of power consumption and my calculations, it may be off a bit

Long story short, get at least a 550W.

 

[ko888]

NVIDIA's minimum system power requirement is based on a PC configured with an Intel Core i7-920 3.2GHz TDP:130W processor.

 

[Guest]

Right ok, I'm really surprised by that as I was told 850w minimum when I was going for a pair or 7970's before I decided on the 690, so I thought 690>2x GPUs.... You get my thinking. But ok less wattage means less money so I could get a higher rated PSU and still be within budget.

 

[Guest]

Best answer selected by chrispy4949.