Does Blender support dual video cards?

Hi. Didn’t see a hardware section so am posting here. I am going to school for media arts and the program we use for 3D is Maxon’s Cinema 4D. I bought C4D because I work third shift so didn’t want to have to deal with going to the lab to do work and so when I wake up at 3 in the morning on Saturday I can get up and do work. My computer has dual video cards that are sli enabled and I learned that C4D does not support that. Does Blender support dual GPU’s? I planned to take the time between classes I have to get some fundementals in 3D animation but I can’t do that if C4D is going to bog down because it is only using half my GPU power. I really don’t feel like buying a single faster video card because this computer is new. Thanks for any replies in advance.

most often it is the operating system (OS) that does not support it, since it wants one interrupt to service the video, and one interrrupt can only be serviced by one card.

If you can get the OS to span the displays, Blender supports it. I have a dual monitor setup but they are both driven off one video card. The original video card is disabled by the BIOS so it is invisible to the OS.

I have only one monitor which is my 32 inch lcd tv. Can linux use both cards at once like it might be using dual cores? I am using Windows right now but have linux on the same machine as well. (FC7) I imagine I’d have to compile a custom kernel. Thanks for your reply.

Nvidias proprietary drivers for Linux has SLI support. So any modern distribution should come with SLI support.

If I understand it correctly SLI should make them both act as one? I just don’t understand what is going on. The file that is choking on my system is running fine on other people’s machines.

“I’ve just tried your file on my old G4 iMac, 1GHz and .75 Gib RAM. It opensin about 2 seconds. I can move about in the viewport, scrub the timeline and all happens is it drops to wireframe for the transition.”

So I don’t understand what is going on. So my thought was if Blender can use my hardware to it’s fullest extent then it would be worth using over a professional program I paid for if that program is going to be limited to one GPU. I don’t want to really go out and buy a new video card to use it seeings how This computer is 4 months old and then I’d have two videocards with no use for them.

To get SLI working, you first have to install nvidia’s proprietary drivers. These can be found on nvidia’s site. I know if you are running Ubuntu you can install them through the package manager, but I am not sure about other distros. After the drivers are installed, you have to modify the file /etc/X11/xorg.conf (this assumes that you are using X11). Check around online on how to do this. Nvidia has this page about their settings in X11.

As far as the SLI mode, you most likely want to use split frame rendering, although I’m not sure if this will help much. Generally, SLI is better for games where rendering can take a long time. Your problems are probably related more to actual video memory. I don’t know if SLI is as helpful there.

Blender runs fine on my SLI enabled rig, both in Win XP and Ubuntu, but I’m not sure if it actually takes advantage of both of the cards.

I hope some of this helps.


each card is a 256 mb card. Is there a way to see how much video memory you have/is being used in windows? Should i have 512 altogether or is only one card being used so I have 256 and that is why? Also my tv is an hdtv (is my monitor as well.) So maybe it is displaying in hi-def and using all my memory? I dunno I’ve seen settings in ntunes for hdtvs. Mine is hooked up via a dvi to hdmi cord.

using SLI for blenders real time rendering is like hunting a humming bird, with a thermal nuclear weapon .

Big overkill.

You can run blender on 2 monitors with a single card. Be sure to try it in windows first so you can see how it is supposed to look, and run. Linux Nvidia drivers are the best on the market… but that is really not saying much, they are still full of nasty little bugs, and are about 5000% harder to install than the windows counterpart.

In windows I can have blender open in landscape mode, on both monitors, in a window… In linux, it will blank out my second window, so that I have to re-size the window frame by 1 pixel in any direction to make it work.

Xorg.conf is a pain to get right. Tho I would recommend using “nvidia-settings” for setting up nvidia specific things. If your using Linux, in Ubuntu its called “nvidia-settings”.

Very useful program. :slight_smile:

LinuxPimp, I have Blender running on a Dual GPU, Dual Monitor system without problem (Windows XP).

I only have my tv as the single monitor. Does dual GPUs work like dual CPUs or is it just so you can have two monitors?

Just so that you can have two monitors.

When using SLI in nvidia you can get a display performance boost due to the GPUs sharing load. You should note that the GPU RAM is not shared so two graphics cards with 256 Mb will be treated as a slightly faster GPU with 256Mb ram (and not one with 512Mb ram).

However two monitors and two GPU’s will increase speed considerably compared to two screens with one GPU.

If your first post is asking about Render speed, then the GPU will have no impact whatsoever (its all about the CPU and RAM your computer has)


thanks for your reply. So I essentially have 256 mb of video memory and an unused card then. My first reply was not refering to rendering but displaying the 3d because my computer was bogging down. Seems like I shot myself in the foot again. So I guess the real question is which handles better with 256 mb video memory? C4D in Windows or Blender in Linux? Is there a reasonable way for me to test this and get meaningful data from?