Sorry if this question is already ask somewhere and answer already provide, if so please point me to the correct place.
I have a machine with 4GB RAM memory and HD5870 with 1GB memory. When I use clGetDeviceInfo to get CL_DEVICE_GLOBAL_MEM_SIZE it only return 3GB RAM in my machine and only 256MB video memory from HD5870 which is actually much smaller than the original value.
At first I though memory used by OS will deducted but end up the value getting was not.
When I try to allocate 140MB memory from HD5870, it fail and said memory not enough. In the end, I was able to use less than 110MB than 1GB memory provided by the graphic card.
I wish someone can tell me what is actually happen, that will be gratefully to help me understanding more in OpenCL.