I'm using AMD Display Library which basically allows us to control certain parameters of the GPU (Clock Speeds / Fan control).
The SDK comes with a Sample-Managed code and I was able to get the required result (Core and Memory clock speeds) from ADL_Overdrive6_StateInfo_Get method.
Using the ADL_Overdrive6_State_Set method (which has the same parameters) returns an error code:
int od_result = ADL.ADL_Overdrive6_State_Set(OSAdapterInfoData.ADLAdapterInfo[i].AdapterIndex, ADL.ADL_OD6_SETSTATE_PERFORMANCE, stateInfoBuffer);
-8 ADL_ERR_NOT_SUPPORTED (Function not supported by the driver.)
I've tested it on a system with AMD Radeon R9 280x / AMD Radeon HD 7970 and a laptop with AMD Radeon 8670M.
Do I need to change something in the driver settings and is there a compatibility issue?
As @novaterata stated in the comment that I could try using the 7.0 library but I moved on to use the Afterburner API http://forums.guru3d.com/showthread.php?t=339656
Contacting AMD didn't help.