Getting a second GPU for rendering in Cycles


I don’t know much about hardware so, please, be gentle!

I’m thinking of getting a second GPU to cut (Blender Cycles) rendering times in half. After some research I found out that:

  • each GPU renders an assigned tile in Blender (hence the reduced half time)
  • the new GPU has to be of the same type (Nvidia, in my case)
  • Two GPUs can generate more heat
  • ‘I need to check the power’ (not sure what that means)

I own a
‘GA-X99P-SLI LGA2011-3 ATX’ Motherboard, with a
‘Palit Geforce GTX 1070 Super JetStream 8GB GDDR5’ Graphics Card, and a
‘NH-D9DX i4 3U 92mm Intel Xeon’ CPU Cooler

Here are my questions:
A. Should i get the same GTX 1070 or should I go for a faster one (e.g. the 1080?) I was thinking of buying the same GTX 1070.
B. In terms of heat, will the PC be ok or should I do something about it?
C. In terms of power, what should i do?
D. For rendering in Blender, do i have to physically connect the cards via SLI, or they don’t need to be connected?

Many thanks for any comments and help,

Moved from “General Forums > Blender and CG Discussions” to “Support > Technical Support”

“Need to check the power” means that you need to list the one item you didn’t: What power supply do you have? High end graphics cards draw a lot of power and depending on what power supply you have, it may not be enough to support two graphics cards. You also didn’t list your CPU which is the second highest power draw in a computer. Your CPU cooler doesn’t mean anything, it only cools the processor. As far as cooling, the GPU handles that itself, you just need to get the hot air out of the case(so fans to draw cool air in from the front and a fan at the back to push it out, depending on the case you have, it may already do this).

The cards don’t have to be connected to use them in Blender.

Although I’m no expert here are some answers for you:

  1. Your choice of card is totally dependent of your budget. You can ( at least theoretically ) mix whatever you want. Since render times scale well for GPU you will (most likely) reach your goal in reducing time by half when getting the same card. A 1080 will most likely cut render time even more but will also use more power ( See also point4 ).

  2. Your CPU- cooler will most likely be of no problem. More of interest is the overall Airflow within your case. ( Read: Can your case fans provide enough fresh air and transport the heat out into the free. )

  3. You have to sum up the power consumption of all your components and make shure your PSU is sufficient. ( Beware of energy cost at your location!)

  4. No SLI needed for Cycles rendering. ( I even have something on the back of my head, that it has negative effects on Cycles speed. But I’m not sure on that.

I hope this is at least a bit of help.

Edit: Ooops, Obsurveyor answered while typing…

Regarding power, my PSU was not strong enough and instead of buying a new 1200W PSU or something I used this:

and an old PSU I had lying around. It looks a bit wonky with the second PSU on the outside of the case but it works like a charm.

Now this is interesting. Could resurrect some old parts in my next build I’m planing. Thanks for sharing!

Hi people,

many thanks for your helpful comments - things are already clearer. These are the components of my PC:

GA-X99P-SLI LGA2011-3 ATX Motherboard

Xeon E5-2630 v4 2.2GHz 85W 25MB 10 Core LGA2011-3

Corsair DDR4 Vengeance LPX 128GB (8x16GB) 2400MHz Memory Kit

NH-D9DX i4 3U 92mm Intel Xeon CPU Cooler

Palit Geforce GTX 1070 Super JetStream 8GB GDDR5 Graphics Card

be quiet Pure Power 9 Modular 700W 80+ Silver PSU

Samsung PM961 256GB Polaris NVMe M.2 SSD

Since I won’t have to physically connect the GPUs together, and the cards won’t have to be identical, my decision will be based entirely 1) on my current PSU and 2) budget.

Apologies for initially posting in the wrong forum.
Many thanks again!

The PSU is 700W and and the CPU is the Xeon E5-2630 85W.

Any more thoughts if it will be ok to add the 2nd GPU?

Thanks again!

If it’s just another 1070, and you don’t have a ton of mechanical drives, 700W should be fine.

Keep in mind to check if you got enough space in the case and the slot next to the GPU slot is free.

Oh yeah, good point. Your motherboard has to have another 16x PCIe slot to put it in as well.

are you trying to start a fire? these things are not to be messed with. improper use of power supplies can cause them to go up in smoke. its happened to me twice. lucky i only lost a hard drive.

if you are adept in electrical engineering and want to experiment fine, but dont suggest this as a real solution for the average user.

high quality psu’s have better protection against surges and more stable voltage at various loads to make sure your fancy hardware lasts as long as possible.

you might even void the warranty for “improper installation”.

It’s not going to start a fire. Using that circuit board is the safe way to do it, rather than the stupid ways like using bits of wire or paperclips(!!!) to short the power on signal pin which is the usual Internet suggestion.

I’ve been running this circuit for 1,5 years, nearly every day for 8 hours and I did not have a single issue ever. So while you are completely right to say not to mess with electrical equipment until you know what you are doing and are prepared to destroy it, in this case this is a commercial, tested product and I have no issues recommending it.

That’s a good point, I checked and I don’t think there is enough for the exact same GPU. Is there a 1070 variant that is physically smaller?

Any ideas if the EVGA GTX 1070 FTW card would work with my setup? It does look physically smaller