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jstier
Journeyman III

multiple GPU

clGetDeviceIDs only returns one GPU

Hi, I have two HD 5830 in my PC but a call to clGetDeviceIDs only detects one of the devices. According to the device manager on Windows 7 (64) both devices seem to be running fine using driver version 8.831.2.0. Am I missing something here? Are multiple devices already supported?

 

 



 

 



 

 





 





 



 

 



 

sStatusCL = clGetDeviceIDs(lPlatform, CL_DEVICE_TYPE_GPU, 100, lDevices, &lCount);

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21 Replies
nou
Exemplar

multiple GPU

you should have connected monitor to both cards and have extended desktop. becuas windows disable disconnected card.

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jstier
Journeyman III

multiple GPU

Are you 100% certain about that, because the device manager under windows lists them both. I do not have a second monitor handy right now to try this out, but is there a way that I can tell windows to enable the card anyways? So basically, I cannot use multiple GPUs for HPC under windows ?



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nou
Exemplar

multiple GPU

well most of the monitors have two inputs. like DVI+DSUB or DVI+HDMI. so connect both card into one monitor.

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davibu
Journeyman III

multiple GPU

Originally posted by: jstier Hi, I have two HD 5830 in my PC but a call to clGetDeviceIDs only detects one of the devices. According to the device manager on Windows 7 (64) both devices seem to be running fine using driver version 8.831.2.0. Am I missing something here? Are multiple devices already supported? 

 

 



 

Are they connected with a CrossFire cable ? It may be the source of the problem.

 

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jstier
Journeyman III

multiple GPU

No, they are not connected by crossfire. It must be something along to lines of what nou says. When I start our App, clGetDeviceIDs detects one device and everything runs fine. When I plug the monitor into the other card (no reboot) the same thing happens. App runs fine but only detects one device. It looks like it is always the card connected to the monitor that is detected.  Another thing I do not understand is that when I switch the monitor cable, the windows desktop appears right away. It is almost like the two cards are rendering the windows gui in lockstep. Yet, when I switch monitor with our app running it crashes.

If Windows  7 really disables the unconnected card to the point that even the AMD drivers cannot detect it, then how is it possible that you can run PhysX on a separate card with NVIDIA hardware. Does the PhysX GPU also have to be connected to a monitor? I am curious if someone has a solution beyond plugging in the same monitor into both cards.

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MicahVillmow
Staff
Staff

multiple GPU

jstier,
This is a limitation of our driver model and is something we are working on fixing. The other solutions are to create dummy plugs or use linux for development.
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latigido922
Journeyman III

multiple GPU

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barno
Journeyman III

multiple GPU

MicahVillmow, can you perhaps give some more details on when you expect that to be fixed? We are having the problem that we need to use our computer remotely in which case none of our AMD GPUs shows up as an OpenCL device (even when they are connected to monitors). I figured that originates from the same problem, or am I mistaken?

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laobrasuca
Journeyman III

multiple GPU

are you using Windows Remote Desktop or somtehing else?

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