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OpenCL

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Adept I
Adept I

OpenCl on APU

Hi everyone,

Yes, this is a recurring subject but I did not get a reply on the forum...

My config :

- APU : A8-3870K (with the latest driver )

- Ubuntu : 11.04

- AMD APP SDK: 2.6


My questions :

1 - When i run clinfo, i get  (inter alia):

     Name                         : AMD A8-3870 APU with Radeon HD Graphic

     Max compute units     :  4

     Max clock frequency     : 3000MHz (and sometime 800Mhz)

Well, he found my APU as a device. But  he saw only 4 cores, which corresponds to the CPU part of the APU. Is it a normal behavior ? What about the GPU part ?

Another thing, sometime i have max clock frequency at 3Ghz and sometime at 800MHz. So, i guess that he switch (randomly ?) on the GPU part...

2 - I'm trying to launch a kernel only on the GPU part of the APU. So, i just give the APU's deviceId when i create my context. It works, but i don't know if i really use the GPU part... Is it enough or there is a special trick for do that ? Maybe with "clCreatSubDevices" ?

3 - Is that my questions have meaning ? Is it possible to work only on the GPU part of the APU ?

Thanks in advance for your help,

Guix


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Exemplar
Exemplar

Re: OpenCl on APU

currently AMD APP SDK see APU as two distinct devices. and what you see is just CPU part. you must install catalyst drivers to see GPU too.

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Adept I
Adept I

Re: OpenCl on APU

Hi nou,

thanks for your answer, but I already installed the catalyst drivers (Catalyst 12.2).

Actually, I guess that catalyst is supplied with the APU drivers : http://support.amd.com/fr/gpudownload/linux/Pages/radeon_linux.aspx?type=2.4.1&product=2.4.1.3.42&la...  , Mistaken ?

Thanks,

Guix

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Re: OpenCl on APU

1.) There is nothing random about clinfo. On APU machines clinfo will enumerate two devices CPU and GPU, I suspect 3000MHz relate to the CPU and the 800 Mhz relate to the GPU. Be sure to correlate these numbers with the 'Device Type' entry . 

2+3.) You can relate the device ID to its type by calling clGetDeviceInfo with 'CL_DEVICE_TYPE' parameter or you can create the context using clCreateContextFromType with the parameters: CL_DEVICE_TYPE_GPU/CL_DEVICE_TYPE_CPU/CL_DEVICE_TYPE_ALL.

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Elite
Elite

Re: OpenCl on APU

Did you make sure that the GPU is enabled in the BIOS?

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Adept I
Adept I

Re: OpenCl on APU

Regarding the MHz variations, this sounds like frequency scaling of the CPU. Try to find some CPU monitoring tool on your system that can show the current CPU frequency and compare with what is reported from clinfo. An alternative approach is to run "cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies" and see if the list contains both 800MHz and 3GHz.

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Adept I
Adept I

Re: OpenCl on APU

Ok guys, thanks for your help.

I found what was the problem : My discrete GPU !! (Yes, I should have put this in my config... )

In fact : when my discrete GPU (Radeon HD 6870) is plugged, clinfo finds it and only the CPU part of the APU. But without the discrete GPU, indeed, clinfo finds both CPU and GPU parts of APU (the expected behavior) !

Now, my question is : Is this mean that GPU part of APU is always disabled if there is an discrete GPU in the system ?

I'm sure there is a way to correct that. I found it on the forum : http://devgurus.amd.com/message/1252077#1252077

I will study it and tell you if everything works. But, if anyone has advice, I listen

Thanks,

Guix



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Challenger
Challenger

Re: OpenCl on APU

I've got the same problem on both desktop and laptop systems and posted several times about this issue:

Unfortunately, I haven't had any luck getting both the igpu and dgpu to work concurrently.  I tried changing the BIOS settings for the primary graphics card and using aticonfig to configure the systems, but nothing worked.  It seems that the AMD Catalyst Proprietary Display Driver - Linux x86 & Linux x86_64 (up to and including 12.3) just don't support things like we expect.  If you somehow get it to work please post your solution, as will I.

BTW, I called the AMD technical support and they didn't have any solution.  They said for Linux systems I pretty much have to wait and hope the next driver fixes this problem, but didn't give me any timeline nor issue me a tracking number.   Much thanks to anyone who solves this!

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Adept I
Adept I

Re: OpenCl on APU

You are rigth Nilsson, my "sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies" contains both 0.8GHz and 3GHz and some others. So, the "max clock frequecy" variations are normals for the CPU part of APU.

Thanks,

Guix

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Journeyman III
Journeyman III

Re: OpenCl on APU

Hi,

  I'm also stuck with the frequency issue on the APU, but what I would like to do is to manually set the voltage/frequency for CPU and GPU on a APU. The v/f level for the CPU part can be easily set using a tool like cpufreq, but how can I do it for the GPU part? Does AMD release any tool for this usage?

Thanks,

Ying

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