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Comment by tamrix | Hacker News Reader

If you're using Intel 8th gen or above. (7th gen supported if you manually set the flag each boot) you've got speedshift which the CPU will automatically auto scale itself. (changing the p-states)

The CPU itself can change frequencies much faster on its own instead of the software based speedstep which programs like this controlled.

This eliminates the need for an on-battery or plugged-in performance mode because it changes frequencies so fast, you're no longer losing performance by waiting for the software to speed up the cpu. So you can keep it on all the time.

For these CPUs, all this is in the kernel and enabled by default.

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> This eliminates the need for an on-battery or plugged-in performance mode because it changes frequencies so fast, you're no longer losing performance by waiting for the software to speed up the cpu. So you can keep it on all the time.

Here's my /etc/rc.d/rc.local script:

    #!/bin/sh
    for policy in /sys/devices/system/cpu/cpufreq/policy*
    do
        echo "power" > "$policy"/energy_performance_preference
    done

Here's available preferences:

    $ cat /sys/devices/system/cpu/cpufreq/policy0/energy_performance_available_preferences 
    default performance balance_performance balance_power power

Basically I can choose between "performance" and "power" (low performance) modes. I'm choosing power, so my fans are silent. And they're silent indeed, no matter the load.

  echo power | tee /sys/devices/system/cpu/cpufreq/policy*/energy_performance_preference

for no additional output, sponge over tee! sponge is useful in some cases where redirecting output is annoying, and it can construct pipelines reading/writing from the same file.

Found that one way later than I'd care to admit. I use tee $FILE > /dev/null <EOF quite often in some situations where redirects get ugly, and sponge is a nice util to tidy up the invocation.

Useful, thank you. It appears that this is the setting the Ubuntu / Gnome's "Power -> Power mode" setting changes as well.

For reference, 7th gen is Kaby Lake and 8th gen is Coffee Lake. Of course, Intel had stagnated long before so many people are still on Sky Lake (6th gen).

I believe that feature was just litigated in VLSI v Intel. VLSI won 2.1 billion in damages due to their patent.

The patent system is so useful, charging vendors billions of dollars for implementing an idea like “use the most obvious possible power saving strategies”.

The patent system also helps small companies with little working capital get started on big, obvious, money intensive challenges without being immediately crushed by megacorps. The razor cuts both ways.

Yes, this is the truth. Look at the recent Cisco patent case. They pulled a Facebook and stole some startups IP while meeting with them. The startup won over 1.5 billion in damages, mostly because they were able to show willful infringement on Cisco's part.

https://www.ipwatchdog.com/2020/10/09/centripetal-networks-a...

Why does Windows do on-battery/plugged-in performance modes on Microsoft hardware with 10th gen i7?

most of it is brightness related thing and i understand there are various inner settings but I find them doing very little. So it usually doesn't bring value to the table.

In theory it could inform programs like messengers to behave battery friendly. In practice I don't think that is implemented.

Is the same true for Ryzen CPUs?

I had a look and https://www.tomshardware.com/uk/reviews/amd-ryzen-9_3900x-vs...

"AMD’s Ryzen 9 3900X also has the new Collaborative Power Performance Control 2 (CPPC2) feature, which manipulates Ryzen 3000's power states from within the operating system. This is similar to Intel's Speed Shift technology and reduces power state transition latency. Ultimately, that results in a more efficient processor during all facets of operation."

Though that seems to be about boosting clocks higher clocks when it can.

https://www.amd.com/en/technologies/smartshift

Again does seem to focus upon boosting performance

So no clear-cut stand-out answer, but does seem some level of OS interaction is required, I couldn't say with 100% certainty.

SpeedShift is from Skylake so 6th, isn't it?, or is there any Linux specific limitation?

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