OpenCL on Linux with multiple ATI GPUs

Hi there,

I’m in the process of setting up a computer with two ATI Radeon HD 5970 cards, i.e. it has four GPUs. I’m running Linux and I’ve been able to install the ATI driver and also the AMD Stream SDK. The aticonfig tool shows that all GPUs are detected and running fglrxinfo tells me that the ATI driver is being used.

However, when I run OpenCL applications, only one GPU is detected, probably the one that my monitor is connected to. I’ve tried enabling the other ones using “aticonfig --adapter=all --initial” which creates a xorg.conf file that contains four device section, four monitor sections and four screen sections that each connect one device (graphics card) to one monitor. When I log on to my system though, the display goes crazy and kind of keeps flashing and is not usable at all. I’ve tried this on both OpenSUSE 11.2 and Ubuntu 9.10 with the same result in both cases…
I’ve also tried to run the OpenCL apps in text mode, but there only the CPUs are visible.

Is there a way of activating the remaining GPUs without assigning them to a monitor? Or some other way of making the GPUs available to OpenCL?

Thanks in advance

OK. I fixed it myself :slight_smile:

Here’s some information in case someone runs into the same problem:

It was some problem with Gnome. It only worked when I logged in as root, but not as a normal user. I then tried xterm which worked fine with both root and normal user.

In every case it is important to set DISPLAY to “:0” though:

export DISPLAY=:0

Otherwise only one GPU is detected by OpenCL

Interesting, thanks.