SLI GTX 770 4GB - Appropriate PSU?

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Omga4000

Omga4000

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Hey all :)

I've read in many places you should get at least 750W to power the GTX 770 in SLI,
yet some have told me it's way too much, and that the computer won't actually use this much.

I have the SeaSonic X-660W, which is a fairly good PSU, but is it enough?

**Should be noted: I'm waiting for the GTX 800 series to come before I make this upgrade,
and usually newer generations have better power consumptions, though by not much.

Thank you,
Omga4000 :)
 
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Omga4000

Omga4000

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No, sorry. Though I understood Amps are less important than the total W.


Be safe from what? What happens if I try to run them with my current PSU?
 
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Spectre694

Spectre694

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Odds are that PSU is going to give up on life if you try to run it and it can't give enough power possibly taking something with it.

and the Amps tell you how much power (watts) are available to each part of the system
 
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IDontUnderstand

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You can probably boot the system up with your current PSU, but chances are that when you start a game or some processors intensive application, the PSU will most likely fail to deliver enough wattage. And then it could either just shut down and nothing is damaged, or burn the PSU and lit fire on everything else (there are stories like that everywhere just by googling). However, with a PSU from Seasonic, the situation will be closer to the first rather than the second scenario, but once again, it will most likely not be able to deliver enough wattage and force you to do nothing, but surf the web.
 
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Omga4000

Omga4000

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Isn't there a safety feature that shuts down the system BEFORE causing damage to parts?
The 12V is 54A, giving out a maximum of 648W.


Do you have a site that has been testing the true power consumption of the GTX 770?
 
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IDontUnderstand

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enemy1g

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Amps are the important factor and determine what your actual wattage is.

If I recall correctly, a PC with a single GTX 770 requires about 40A to a 12V rail. If you're factoring in a second GTX 770; at about 250W peak consumption, you're adding ~21A to your total usage. Bringing you to the minimum of 61A to a 12V rail, which would equate to about 732W. 750W has been said that it is the sweet spot for SLI 770s.
 
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Omga4000

Omga4000

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http://www.guru3d.com/articles_pages/geforce_gtx_770_sli_review,4.html
400W Used? Confused..


http://www.guru3d.com/articles_pages/geforce_gtx_770_sli_review,4.html
400W Used? Confused..
 
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IDontUnderstand

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Yes indeed it says 400W used, but keep in mind that GPU isn't the only component that uses power within a system. A typical CPU can draw power from 100 up to 250 ish or even higher depending on the CPU. In addition, the motherboard also draws power, so does fan, HDD, optical drive, etc.
Furthermore, even if you add up all those wattage and still end up under 660W, it's still not good enough, because PSU are not meant to run at 100% or even close to that in any situation. PSU efficiency is best when under 50-70% load. As you can see in http://en.wikipedia.org/wiki/80_Plus that all the ratings go down compare from 50% to 100%.

Therefore, it's always better to go at least 20-30% more wattage than the actual maximum power draw. 20% because components are very unlikely to ever reach max power consumption unless under stress test, but once again, 20-30% more than actual estimation by adding the wattage on yourself is the best.
 
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Spectre694

Spectre694

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400W(possibly for them to briefly pull up to 500w) is what is used by the cards and nothing else once you factor in CPU HDD etc your requirements increase even more. especially with overclocking which is not linearly added to the power draw but more exponentially. plus you want to add a little in for safety to make sure your PSU isn't running at 98% or some other absurd load. Which is why they recommend 700-800W PSU right in line with enemy1g's calculations.
 
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Spectre694

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The safety mechanisms are to prevent surges from the PSU to the components there is not really a way to prevent a component from trying to draw as much power as it wants from the PSU other than killing the PSU itself to prevent damage. Thats why cheap ones burn they keep trying to supply more power than designed for and simply overheat and burn. More expensive ones usually just fail altogether.
 
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Omga4000

Omga4000

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Just specifying my specs real quick:

CPU: i5 3470 (no OC)
Motherboard: Gigabyte B75M-D3H
HDDs: 1x500GB WD Green
...........1x1TB Seagate Barracuda 7200.14
Fans: 3 in total (1x120m, 2x140m)
RAM: 2x4GB 1600MHz (8GB Total)


I've listed my system spec in this message. Please review them.


Thank you for the lesson :)
 
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Spectre694

Spectre694

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Quick and dirty for worst case scenario take the TDP and add them up.

CPU: 77W
HDD: 25W (startup) x2
Fan: 5W x3
GPU: 250W (peak) x2

Equal 642W

Round to 650 and add 30 for mobo chipset RAM and your at 680W

Meaning minimum you want is a 700W PSU 750W should put you at about 90%. Doable but not efficient

Efficiency you want 50-70% puts you at 1000W (68%)

Pick the total wattage based on budget.
 
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Omga4000

Omga4000

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Well I'm not going to stress test it all day.. It will only reach those places on gaming, so I don't care if it
works on 90% when I'm gaming. Completely fine by me.



I was thinking of getting the FSP Aurum 750W Gold, Which has a 72A +12V Rail.
Or the SeaSonic X-850W Gold which has a 70A +12V Rail, and more total W.

The SeaSonic is about 15$ More expensive so it doesn't come to pricing.
What do you guys think?
 
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IDontUnderstand

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Even though FSP Aurum 750W Gold is a high quality, but it isn't as high as the SeaSonic.
I would go with SeaSonic X-850W Gold for better quality and modular, but FSP will still do a great job if price becomes a concern.
Source: http://www.bit-tech.net/hardware/psus/2013/04/26/best-power-supply-psu-720-750w/6 (it has review of X-750W on page 8)

If I may suggest other option, a very very high quality PSU, similar quality to SeaSonic (Seasonic is the parent company of XFX, funny)
Source: http://en.wikipedia.org/wiki/XFX#Power_supplies
XFX Black Edition 850W Gold rating http://www.ncixus.com/products/?usaffiliateid=1000031504&sku=78945&vpn=P1-850B-BEFX&manufacture=XFX
Source: http://www.eggxpert.com/forums/thread/323050.aspx
Source: http://www.legitreviews.com/xfx-pro-series-850w-black-edition-psu-review_2239/8
Source: http://www.hardocp.com/article/2009/12/10/xfx_black_edition_850w_power_supply_review/9#.UyD6OPldVfA
Source: http://www.hardwaresecrets.com/article/XFX-PRO-850-W-Black-Edition-Full-Modular-Power-Supply-Review/1716/13
 
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Omga4000

Omga4000

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XFX Would be my choice, but unfortunately I don't live in the USA and no one is selling their
products in my country. Too bad.
 
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