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Hello, i want to buy 3 more GTX 780 6gb in order to have 4 GPUs. My motherboard is Asrock Z87 Extreme4. My current PSU is seasonic 620W. I guess i should buy a new PSU to sustain all 4 GPUs.

What PSU should i buy? How powerful? My cpu is haswell i7 4770k.

Thank you

With 4 780s personally I'd look at around 1500W to be safe on peaks.

Yes I think you should take 1500 for safety
I use 1500watt for 3 X 780ti and 1 680 4gig

I have 1500W for 4x 580's, and came to that asking advice on this forum,
so my advice fornyou is also to go for 1500W

Thank you all for you answers! I would really like to buy a seasonic PSU, because i think they are very good, but the highest voltage they have is 1250 (http://www.seasonicusa.com/NEW_X-series_1250XM2.htm). Would this be enough?

May be. Seasonics can usually be overdrawn by quite a bit and run solid still. I use a Seasonic P860 myself for my two 780ti.

Sidenote: 4 GPUs side by side get very hot and loud. Think of how to cool them. Also: my workstation motherboard has an extra power connector to supply extra power to the PCI *slots*. The manual claims, that with 4 powerful cards, they sometimes draw too much from the slot ... not from the attached PSU cables. I'm not sure how relevant this is and how your asrock willr eact to 4 powerful cards.

If you can, definitely plug in the extra molex for the pci slots. The atx connector may not handle everything

Hi Pavel,
The 1250 is a risk worth taking in my opinion since Octane draws less power, even at full speed, compared to gaming. There are some posts on this. My own theory is that this is because Octane has less intensive RAM usage compared to many other apps.

The risk is at startup due to the initial power draw - you're on the edge there. But I think modern PSU's handle startup better these days. Your other risk is if you plan to use the unit for intensive gaming, which draws more power. But if your machine starts up ok and you only use Octane you should be fine.

Also, don't forget your dedicated display GPU. If you use all your slot space for those gorgeous TI's and Octane, you will have a poor responsiveness from other apps while rendering. You probably know this. I'm just wondering how you plan to solve it.

Best,
Seeker

I guess i will buy a 1500w PSU since i also have an I7 4770k overclocked to 4.6 and that draws power also. What 1500w PSU do you reccomend? Is Enermax Platimax 1500 good?

For cooling and noise i have an Antec p280 case which is pretty silent and has 7 scythe slipstream 120 2000rpm case coolers installed. For CPU i have 2 Noctuah NH-D14 coolers. I have a cooler controller to control the rpm for case coolers in order to keep the noise low when there is no need for cooling.

I don't know if i have an extra power connector on my Motherboard, i am pretty new to PCs, because i have owned a mac until recently. I will find out if i have that extra power conector and let you know. I will seek some local help to install the GPUs and make it work, i guess.

Do you think that my case and motherboard is suitable for 4 GPUs?

Thanks

I have the second power connector, but i have 3 x PCIe 3.0 x16, 2 x PCIe 2.0 x1. Can i install 4 GPUs on this motherboard? (Asrock Z87 extreme4) A local shop guy where i went yesterday said i cannot connect any GPU to PCIe x1 but on Asrock says it supports quad Nvidia SLI. Can you please enlighten me? Thanks