Was wondering about this since different windows versions give me different idle speeds on balanced power profile. (Using Core Temp as reference for clocks) using a 5950x
(I'm not great at poll making)
Thanks for reminding me to reinstall CoreTemp. I've just installed 24H2 on this because microsoft weren't offering it as an update and I need to validate a couple of rendering apps on this version.
As for your idle speeds question, "yes to all" which is technically correct but entirely unhelpful.
Your idle speeds have very little to do with your CPU or OS and far more to do with which and how many services and applications you have installed. The amount of background crap running on a modern PC is insane and even though most of it demands very little of your CPU, there are hundreds of services and background apps that mean your CPU will almost never be idle.
Windows task manager, and even tools like CoreTemp or HWInfo aren't fast enough to catch the very rapid frequency changes of Ryzen's rush-to-idle default behaviour in most power plans. Even AMD themselves say that Ryzen Master isn't fast enough, but it paints a much better picture of the true clocks at any given moment than the aforementioned third-party utilities.
What's actually happening is that Ryzen is suspending cores (effectively 0MHz) to save power, but they're
so suspended that they're not even reporting their clocks which means utilities tend to just assume they're still at the last reported clock. Task manager takes an average of
known clocks, which means it is already out of date for all suspended cores and therefore inaccurate. CoreTemp, I think, looks at the slowest active core and reports that, which is closer to accurate for any given instant but still likely missing the correct values for near-idle states.
Knowing your idle clockspeed is basically useless, because on any modern Ryzen, the real answer is "0 MHz for suspended cores and at least the base clock is for the 0%-1% active core that's currently awake and rushing-to-idle as designed". If the tool you're using reports a different value, you're just seeing the error of the tool.