Multi GPU low performance (GTX Titan Z)

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1

Hello. I’m heading with some performance problems Rendering with Cycles. I’ve a Titan Z and if I do a render with one GPU only (A or B) it does very well. But when I activate Titan Z (x2) in User’s Preferences, the performance is very weak :frowning:
I’ve noticed that in only one GPU, it can do a 99% Load (independent of GPU I choose), but in multi GPU only do 20~40% each! So rendering with 1GPU I have 50% more performance than 2. What is happening here!? :confused:
I’ve no PSU problem, lasted nVidea drivers and used the last Blender version. Windows 8.1

Thanks for you attention

2

Not sure how the Titan Z works…
But since it is basically two Titan Blacks soldered into one casing, could it be possible that they are treated as a SLI bond internally? SLI is not recommendable for GPU rendering because of massive performance issues.

Try browsing through the settings of the Titan Z’s graphics driver: Any option to switch off SLI?

3

Hi, first come in my mind is, have you SLI enabled?
Can you render my benchmark?

http://www.blenderartists.org/forum/showthread.php?350975-The-new-Cycles-GPU-2-72-Benchmark

There is a spreadsheet on last page so you can compare with the Titan entries.
Cycles scales well with 2-4 cards so Titan Z should be a beast. :slight_smile:

Cheers, mib
EDIT: Hey, IkariShinji was faster. :stuck_out_tongue:

4

Mother of God. It’s solved :cool:
Well, the Titan Z doesn’t have a SLI option (since is the only graphic card), but have surely a similar system called, ordinarily, "Multi-GPU. After turnning off “Multi-GPU”, a beast was born :cool:
Thank you very much guys for the hints!

titan_z_multigpu.png710×626 32.2 KB