Not sure I think using AVX512 makes sense in an RNG unless you're already using those instructions for a lot of stuff. Using instructions from outside the current power bin will adjust the clock rate and frequency of the core, and doing so is very slow (measured in milliseconds -- voltage regulators need to adjust).

In general unless you have a lot of AVX512 code to run (several ms worth), you're usually better off avoiding those instructions IME :(. (The same is also true for many AVX2 instructions...)

(See https://en.wikichip.org/wiki/intel/frequency_behavior#Base.2... for some more info, as well as the Intel optimization guide).