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Carlos Fenollosa

Carlos Fenollosa

Engineer, developer, entrepreneur

Carlos Fenollosa — Blog

Thoughts on science and tips for researchers who use computers

Slow down your laptop

August 27, 2019 — Carlos Fenollosa

800 Mega Hertz is enough (via) argues that for most use cases laptops don't need to run at their top speed to save battery.

Computers are amazing; they are so fast and can do so much. Nevertheless, what if we didn't need it to be so fast or do so much? That was the question I asked myself when I was trying to improve the battery life of my laptop even further. I came up with a simple solution. The processor that came in my computer runs at 2.2GHz, that isn't fast compared to modern laptops today, but it is still much faster than I need it to be. Each clock cycle uses a little bit of power, and if all I'm doing is typing out Latex documents, then I don't need that many clock cycles. I don't need one thousand four hundred of them to be precise.

The only caveat is that modern web browsing is definitely much more taxing than "typing out latex documents." You are running almost an entire graphical OS in each tab. And, if I'm not mistaken, most frequency managers actually slow down CPUs to a crawl when they're idle. Other than that, I'm all in on this.

In my own experience, disabling Turbo Boost is barely noticeable and extends battery life for about an hour, which translates to around 20% extra life. I actually have a script called lpm.sh, for "low power mode" that essentially stops syncthing, an important source of CPU wakeups, and disables turbo boost to grant me those extra minutes. CPU frequency is properly managed in my case and I don't have the need to run cpupower manually.

If you truly want to run the most resource-constrained, "distraction-free typewriter mode", boot into single-user mode and write using vim.

Bonus rabbit hole of the day: CPU power management

Tags: hardware, minimalism

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