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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?


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