I have a 3940XM CPU in my laptop. Behaves strangely with windows 10. (speedshift over speedstep issue? )Why do IDLE states turn off when certain programs run?

[JWils51]

CPU Passes all Intel Tool CPU tests. Win 10 balanced profile used. PowerCfg /SETACVALUEINDEX SCHEME_CURRENT SUB_PROCESSOR IDLEDISABLE 000 script is the only way to turn IDLE states back on after being toggled "off" due to running certain browsers and programs. For example, Opera, Edge, and some programs. The browser works fine and IDLEs after script run. IDLE weirdness doesn't occur with Firefox or regular Microsoft apps. Some in other forums complain about IDLE issue due to VR which I am not using. Have clean installed OS and toggle dspeedstep in BIOS, etc. No luck. Win 10 compatibility issue with this processor?

[Gh0stb1t]

The processor is supported for Windows 10, what specific Windows 10 builds are supported is a different questions. The are drivers for its graphics, but this CPU and graphics are old and turning into Lecagy models.

However, the latest driver might not include any "real update" or improvement but only some security fixes.

The SpeedStep and Speed Shift are technologies supported by the processor, but the implementation and control is in the BIOS, if any issue is arising from them, you need to check with your laptop manufacturer. I would check if have a BIOS update pending and check if the updates included in the firmware can solve this behavior. Also, the CPU is passing all tests so this is another clue where the root cause is not coming from.