I think I now understand how this works. You can click on "Configure switchable graphics" from the CCC tray icon and then explicitly assign either "Power-saving graphics" (which I assume is integrated graphics) or "High performance graphics" (which I assume is discrete graphics) to your application exe. Changing this assignment causes different performance for my application as expected. It is disappointing that I cannot use both the cards. Under OpenCL, both are exposed as separate devices and I can use both. On Nvidia based systems, I can use both the Intel HD graphics and Nvidia graphics as separate adapters for DirectCompute.