I have no idea when people started saying is a 30% hit on the cpu! In reality is average of <=5% : https://www.reddit.com/r/pcgaming/comments/7o2ctw/benchmarke...

EDIT: found it! 5-30% as reported by theregister : https://www.theregister.co.uk/2018/01/02/intel_cpu_design_fl...