What are requirements for HEVC/h265 encoding?

I've i3 6100U, which is Skylake with HD 520 iGPU. I read elsewhere that Skylake supports HEVC encoding, but VideoProc reports it as unavaliable. (while h264 is fully available, i.e. 4k high@5.1)

(yes, it's a minor thing, but I strive to perfect my hack)