First thing i do on w10 is kill defender.Counter Control is a small program that will monitor the fixed performance counters on Intel processors.
Microsoft's Windows Defender anti-virus software will sporadically take over all hardware performance counters and use them in a way that reduces system performance significantly. Using Counter Control you can identify this and mitigate it. Source
article says its a bug, gotta be otherwise amd amd would be affected too.not a surprise really, it is a realtime scanner afterall