Power supply needed for a GTX 980 SLI (2x) system?

LogicalCaveman · Jul 6, 2015

First off, sorry if this thread is in the wrong forum. I figured since my question is directly related to GTX 980 SLI, the graphics cards experts could help me the most.

I'm building a computer system during next year's (2016) Black Friday deals. The specs of the system I'll build are below.

http://pcpartpicker.com/p/QycydC

In the initial build, I likely won't overclock my i7-4790k, and will only be using a single GTX 980.

However, the system will eventually have the i7-4790k overclocked decently and include two GTX 980s that may or may not be overclocked. In the initial build, I want to get the power supply I'll need for this final build.

Please keep in mind that I have an absolute funding maximum of $1800 USD, so any changes MUST be below that price. Lastly, I don't want to just barely power this system. I want to have more than enough power to avoid any issues with the system not getting enough power in a worst case scenario.

So in conclusion, I ask you this: what kind of power supply will I need to power the overclocked i7-4790k and twin GTX 980 system?

Thank you guys so much!

TechyInAZ · Jul 6, 2015

850W should be fine for 2 980s. If not then go for 1000W (if you want to overclock the cards very hard).

LogicalCaveman · Jul 6, 2015

Thank you for responding, TechyInAZ!

How significant of an overclock on the cards (I assume you mean the graphics cards and not the CPU?) would warrant a 1000W PSU?

Dunlop0078 · Jul 6, 2015

I think 850watts should be plenty and that evga supernova G2 you have there is a very good power supply, that's what i would recommend.

Dunlop0078 · Jul 6, 2015

LogicalCaveman :

Im pretty sure you could overclock everything, your cpu, gpu's and still have plenty of power to spare.

JackNaylorPE · Jul 6, 2015

Nvidia power supply requirements can be found here:

http://www.tomshardware.com/answers/id-2311121/power-supply-requirements-nvidia-gpus.html#14243229

Budget PSUs:

$80 EVGA B2

Very Good PSUs

$120 EVGA G2 850
$130 Corsair HX 850
$140 Seasonic X-850 / XFX P1 850

If water cooling and overclocking everything to the max, ya might wanna go for a 1050, and if ya want it to be gorgeous, the Seasonic 1050 Snow Edition comes close to being geek porn

LogicalCaveman · Jul 6, 2015

Thanks for your response, Dunlop0078!

I, too, was originally thinking a quality 850W PSU would cover the system, but I do intend on aiming the initial system for maximum cooling (i.e. $100 CPU Cooler, etc.) so that I can decently overclock the three cards (CPU, 2 GPUs) later on when newer and newer generations of games put even a 4790k and GTX 980 SLI to the test. After what TechyInAZ mentioned, I wonder if 850W will be enough for said overclocking.

LogicalCaveman · Jul 6, 2015

Interesting link, JackNaylorPE. Thank you.

So, assuming I am reading that chart right, it says 685W PSU would power a system would two stock clocked GTX 980s in a system. How significantly does a decent overclock skew this?

I'm not too experienced with overclocking yet, so I don't know what I need to expect power supply wise to power two overclocked GTX 980s along with an overclocked i7-4790k.

Dunlop0078 · Jul 6, 2015

LogicalCaveman :

I think it is. Maybe not totally ideal but im pretty sure that psu will take an overclock of both cards and the cpu with stride. Maybe if you start messing with the firmware of the 980s to overvolt them you might go over 850watts i still doubt that however.

LogicalCaveman · Jul 6, 2015

I think, unless I see anything warning me not to go 850W between now and then, I'll just go with the EVGA 850W PSU I had in the original link. Thank you guys.

TechyInAZ · Jul 6, 2015

LogicalCaveman :

It's pretty serious, basically pushing voltages past what MSI afterburner has on it via using a custom bios. Kinda like the KINGPIN cards.

JackNaylorPE · Jul 6, 2015

LogicalCaveman :

Well the power slider goes up to 122%

http://www.guru3d.com/articles_pages/msi_geforce_gtx_980_gaming_oc_review,26.html

With AfterBurner we applied:

Temp Target 80 Degrees C
GPU clock +170 MHz
Power limiter 122%
Mem clock +470 MHz
Volatge + 87Mv
FAN RPM 50% (remains silent)

And they measured 198 watts "at the wall"

http://www.guru3d.com/articles_pages/msi_geforce_gtx_980_gaming_oc_review,7.html

198 watts "at the wall" is about 178 watts of PSU output to the card. So adding 22% means an extra 39 watts per card.

685 + 39 + 39 + 52 watts (OC'd CPU) = 815 .... though you will never see both CPU and GFX cards at max at same time. Note that's not an actual load, the recommendation includes capacitor aging and a reasonable cushion

JackNaylorPE · Jul 6, 2015

Internet burped....double post

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