AMD 7970 reporting incorrect DEVICE_GLOBAL_MEM_SIZE

Question

I'm testing some OpenCL image processing on an AMD HD 7970 (Sapphire GHz edition). This particular card has 6GB of RAM onboard, however this call:

clGetDeviceInfo(device, CL_DEVICE_GLOBAL_MEM_SIZE, sizeof(buf_ulong), &buf_ulong, NULL);

returns a value of 2,147,483,648.

Is there an issue with this OpenCL call for returning the actual memory size of a card? Is there some sort of setting for this card that limits the amount of OpenCL memory that can be used?

Any insight would be helpful!

Answer 1

My HD7970 (3GB version, Sapphire GHz edition) reports 2GB of free memory too. It is quite normal to reports less memory than the total amount (OS and driver have to reserve some memory) however your value looks really too low for a 6GB version.

On older AMD drivers was possible to set the amount of memory reserved to OpenCL via a couple of env. variables. However, it is a features that has never been officially supported and I'm afraid it is not available anymore on the latest drivers.