Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm using Ubuntu 12.10, AMD 12.11 beta drivers, AMD APP SDK 2.7 and OpenCL. I have three amd radeon 7990s plugged in each of which are a dual 7970 so I have six gpus altogether. I plan to go up to eight in a few days. Windows couldn't use even 4 but linux works fine with 6 so far.

The strange thing is that the six gpus are only detected by OpenCL in unity (the ubuntu default window manager). If I switch to e17, blackbox or fluxbox or anything else for that matter OpenCL only detects one. I'm using a simple OpenCL program to list all devices to check.

I've also checked the output of aticonfig --list-adapters, fglxinfo and clinfo. The first two always show six in all window managers wheras clinfo shows 6 in unity but 1 gpu in all other WMs. I'm also using an X config generated by aticonfig --initial -f --adapter=all. I'm also only using one monitor. I've also checked using lsmod that the fglrx module is loaded in all WMs.

So I have two questions.

  1. Why does OpenCL see six gpus only in unity?
  2. How can I enable six gpus on other lightweight WMs?

Basically I'm getting at what determines how many gpus the OpenCL runtime sees?


share|improve this question

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.