I get the error CL_INVALID_PLATFORM if I try to run the official samples with the CPU (both my iGPU and discrete GPU work fine with those). The CPU in question is i5 7300HQ. It should support OpenCL 2.1 even, so I assume that it has something to do with the OpenCL runtime. I have installed the recommended Inte SDK for OpenCL applications. Should I have installed the CPU runtime additionally? However it refuses to install in the presence of the graphics one.
On an unrelated note, the VS integration of OpenCL somehow managed to break VS, so I had to disable it. I am unsure whether that's a known bug, but VS kept restarting until I disabled the integrated features coming with the OpenCL SDK.