Finding Out How Many GPU Cores We Have Under Linux, Revisited!

In this earlier posting, I tried to describe in a roundabout way, what the shader cores of a GPU – the Graphics Processing Unit – actually do.

And in this earlier posting, I tried to encourage even Linux-users to find out approximately how many GPU cores they have, given a correct install of the open standard OpenCL – for actual GPU computing – using the command-line tool ‘clinfo’. But that use of ‘clinfo’ left much to be desired, including the fact that sometimes, OpenCL will only assign a maximum number of cores belonging to each core group, that’s a power of 2, even if there may be a non-power-of-two number of cores.

Well, if we have the full set of nVidia drivers installed, nVidia CUDA – which is a competitor to OpenCL, as well as having the nVidia Settings GUI installed, it turns out that there is a much-more accurate answer:


But, this method has as drawback, that it’s only available to us, when we have both nVidia hardware, and the proprietary drivers installed. This could lead some people to the false impression, that maybe, only nVidia graphics cards have real GPUs?



Finding Out, How Many GPU Cores we have, Under Linux

One question which I see written about often on the Web, is how to find out certain stats about our GPU, under Linux. Under Windows, we had GUI-based programs such as ‘GPU-Z’, etc., but under Linux, the information can be just a bit harder to find.

I think that one tool which helps, is to have ‘OpenCL’ installed, as well as the command-line utility ‘clinfo’, which exists as one out of several packages, and as an actual, resulting command-name.

If we’re serious about programming our GPU, then having a GUI won’t help us much. We’d need to get dirty with code in that case, and then to have text-based solutions is suitable. But, if we’re just spectators in this sport, then two stats we may nevertheless want to know are:

  1. How many GPU-Core-Groups do we have – since GPU-Cores are organized as Groups, and
  2. How many actual Shader-Cores do we have in each Group?

Interestingly, the grouping of shader-cores, also represents how many vector-processors such GPU-computing tools as OpenCL see. And so, on the computer which I name ‘Klystron’, which is running Debian / Jessie, when typing in these commands as user, I get the following results:


dirk@Klystron:~$ clinfo | grep units
  Max compute units:                             4
  Max compute units:                             6
dirk@Klystron:~$ clinfo | grep multiple
  Kernel Preferred work group size multiple:     1
  Kernel Preferred work group size multiple:     64


This needs some explaining. On ‘Klystron’, I have the proprietary, AMD packages for OpenCL installed, since that computer has both an AMD CPU and a Radeon GPU. And this means that the OpenCL version will be able to carry out computing on both. And so I have the stats for both.

In this case, the second entries reveal that I have 6×64 cores on the GPU.

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