Go to BIOS, select CPU configuration, allembedded (notebook, laptop, AIO, barbone system, and HTPC) 6th gen intel core comes with base clock and turbo clock, as there're no way to overclock embedded CPU so you can sure your i5 6500 will run at 3.2GHz (base) to 3.6GHz (turbo), the reason why probably you never saw 3.6GHz because apps or program somehow already use all four cores to complete certain task. If you'd like to see 3.6GHz try prime95 tool.