Its mostly due to the way Windows switches threads between cores but also scheduling and OS overhead. You can get a lot closer to Linux if you use software to p

Its mostly due to the way Windows switches threads between cores but also scheduling and OS overhead. You can get a lot closer to Linux if you use software to pin the benchmarking threads to a particular core. The tweaks they did for AMD stop the switching moving from the CCX so often but they don't fix the detrimental effect on cache performance of switching threads to different cores ever 10ms.