Interesting news, it seems that if you own a recent GCN based Pro series GPUs from AMD (Hawaii Pro / Fury Pro / Tonga Pro / etc) is now possible to unlock, at least some of the disabled parts on the GPU.
Over at the OCN forums a user called tx12 released a little utility called CUinfo and this tool can be used to read information about active and disabled CU units in Hawaii, Tonga and Fiji. Basically the tool reads out the GPU core configuration, which can be altered and then flashed back into the BIOS with another tool and some modification. The current status of the tool is that it only reads out info, and you will have to edit and re-flash the BIOS yourself.
Cards like R9 Fury non-X, R9 390, R9 285 could be enabled with more CUs, I say COULD, as there are two methods used by AMD, laser cuts (prevents this from working at all) and through firmware, which would be this methodology.
Be warned though, GPUs are binned, defective CUs could be disabled for a reason, if you enable them ... who knows that will happen. Basically you will be gambling with your graphics card.
Source: OCN Forums