Comment by ancientsofmumu | Hacker News Reader

Comment by ancientsofmumu | Hacker News Reader

This paper relies on Turbo P-states, where they measure the oscillation when that is active; it is not measuring general SpeedStep (OS software controlled) as some seem to have taken away from it. Turbo state is the HWP (hardware P-state controlled) layer above SpeedStep; turning off Turbo in the BIOS still fully allows OS controlled SpeedStep P-states to function, it just disables the hardware level bursting P-states above that max listed CPU level for short periods of time. As others have noted, Turbo state can really kill a laptop battery and/or drive up the thermals pretty quick, a lot of folks disable it anyways if they've tinkered around before.

The abstract writes it as "When frequency boost is disabled, the frequency stays fixed at the base frequency during workload execution, preventing leakage via Hertzbleed. This is not a recommended mitigation strategy as it will very significantly impact performance." This is a confusing grammatical way to state it, as SpeedStep will still work at the OS layer, you'll scale min to max "as usual" and just lose temporary hardware boost max+ capability when under stress (full load at P0 state) - not really "fixed" as it were in layperson's terms. That would be more akin to saying SpeedStep had to be disabled, IMHO.

https://www.kernel.org/doc/html/v4.19/admin-guide/pm/intel_p...

On MacOS Low-Power mode in the Power section of system settings disables turbo-boost. On Linux

    echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo

does the rick. Note that this is not the same as power-saving mode in Gnome settings.

I have found that for heavy C++ compilation that lasts for many minutes the slowdown was about 20% on my ThinkPad X1 laptop. The big plus is that it made the laptop almost silent.

I think you're running into changing the governor mode here, which is a related but different part of the same ballpark. Modern Intel even has a "bias hint" allowed in addition to just a governor, where the user can help tell the power saving features what tradeoffs they prefer; power-saving mode is an additional limitation in conjunction with SpeedStep (or Turbo) P-state use; if the laptop is almost silent (no fans) you're surely clocking it down to avoid heat/thermal buildup (no fans) - this is usually used to conserve/extend battery to the max possible, at the expense of CPU clock speed.

The Arch Wiki has a nice page outlining all of it, there's a lot of knobs to twiddle. https://wiki.archlinux.org/title/CPU_frequency_scaling

It is Gnome Power setting dialog changes the governor. The above command just disables Turbo boost while allowing CPU to spend 100% of its time at the base frequency.

Any way to do it on Windows without getting into BIOS?

You can use tools like ThrottleStop [0]

I use it on my laptop and run it to disable turbo boost most of the time -interestingly for performance reasons. Turbo boost leads to very erratic behaviour on laptops when you have long running CPU-intensive tasks (e.g. the cores run hot and it has to throttle down hard to cool them down again).

[0] https://www.techpowerup.com/download/techpowerup-throttlesto...

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