I have a HD7970 with a monitor connected via DVI. Under Windows 8.1, ZeroCore Power works fine, I can even connect two monitors via active miniDP Adapter and ZCP still works fine (in most cases). Even connecting a 3rd monitor over HDMI does not brake it!
However, after upgrading to Windows 10, ZCP does not work any more at all. Regardless whether I connect a monitor over DVI or any other port (also the active miniDP adapter does not work), power consumption does not change in idle and also the fans don't stop.
I tried all available driver versions for Windows 10, from 15.7.1 until the most recent one, but no difference. It would be nice if AMD could officially clarify whether ZCP officially works under Windows 10 or not and if yes, what one has to do that it works correctly, e. g. with a single monitor connected over DVI?
Could you please be a bit more precise? You say "Windows 10 changed the way ZeroCore works", for me it does not work at all, in any way. If just the way it works has changed, this would mean that it still works in some way. Then it would be interesting to know how it works. If it is not working any more at all, I would at least expect AMD to mention this on its product websites and no longer advertise with a feature that is not working on the most recent operating system!
And could you maybe clarify what changed from Win 8.1 (where it works) to Win 10 causing this issue?
Not sure what you mean, but under all builds of Win10x64 (Currently I am running build 14332 with the 15.11.1 Catalysts as the latest Crimson build doesn't get along with this build), I have found speed (MHz) and power usage fluctuation to work just fine. But with build 14316 I ran the 16.5.1 Crimsons with no problems, and saw no problems with power/MHz fluctuations as they worked as expected.
However, I am running an R9 380 4GB GPU connected via DP-HDMI cabling. My wife's system is the standard, fully updated commercial version of Win10x64 (She doesn't do Insider's builds) with an HD 7850 2GB running the latest Crimsons (16.5.1) and MHz and power fluctuate as expected. Apologize if you meant something else altogether...;)