This has not been proven and my suggestion was somewhat tongue in cheek. So i think it is definitely WAY WAY TOO EARLY to assume that. It may be/likely is just a bug.
But i do think it would be at least worth testing old windows versions for. Based on prior behavior by both Intel and Microsoft.
Either there is some unexplained strategy in the windows scheduler that we do not and never will know about as it is closed source, or its a bug.
Maybe it is some high core count monolithic die strategy thing to distribute CPU temperature across the die to avoid hot spots (so boost can run higher on intel perhaps)? Who knows.
Does the same behavior (thread juggling) happen on high core count intel (but doesn’t hurt it as bad due to inherently UMA architecture)?
Given that this problem appears to be isolated to windows, i think we should be asking the question: “Why?”.
As in “why is windows doing this in its scheduler?”… now that we know what the scheduler is doing to cause the performance regression. There’s quite obviously an algorithm difference between Windows and other platforms here.
It’s either a deliberate algorithm choice due to some benefit on some architectures, it’s an accident or something insidious. There are only 3 options.