Question about the "Power Saver" feature

[Delta]

Hello All!

Does anyone know which MSR the PowerSaver feature changes?

Thanks

 

[unclewebb]

MSR

I think Set Multiplier and Power Saver both write to MSR 0x199. It is debatable how much power the Power Saver feature actually saves. It mostly makes the CPU run at a slow and inefficient speed. Intel CPUs will save more power when the individual cores spend most of their idle time in one of the low power C states such as C7.

Here is an example of 10 cores all running at 5000 MHz. Individual cores are averaging 99% of their time in C7. Idle power consumption is minimal and so are core temperatures.

 

[Delta]

Thanks for reply!

Yes, "Set Multiplier" changes the MSR 0x199 but how does "Power Saver" change it when the CPU is idle?

 

[unclewebb]

There is a value in the Options window you can adjust called PowerSaver C0%. The C0% is a measurement of how active the CPU is. When the CPU is lightly loaded (low C0%) and Power Saver is checked, I think 8 will be written to MSR 0x199. When the CPU is significantly loaded, the maximum multiplier will be written to MSR 0x199.

This feature no longer works on newer CPUs. It was way too slow and clunky to respond to a fast changing CPU. Some users liked it. You are usually better off just letting the CPU control itself.

 

[lexluthermiester]

You are usually better off just letting the CPU control itself.

Good to know.

 

[Delta]

There is a value in the Options window you can adjust called PowerSaver C0%. The C0% is a measurement of how active the CPU is. When the CPU is lightly loaded (low C0%) and Power Saver is checked, I think 8 will be written to MSR 0x199. When the CPU is significantly loaded, the maximum multiplier will be written to MSR 0x199.

This feature no longer works on newer CPUs. It was way too slow and clunky to respond to a fast changing CPU. Some users liked it. You are usually better off just letting the CPU control itself.

Thanks. So the software itself controls the multiplier, not the hardware.
I use that feature on my old 2015 MacBook Pro. The multiplier is locked due to the bad battery.