18 Nov 2019

You’ve been there - after putting your backpack in a frigid car, walking against the Wisconsin wind, or biking across the frozen lake, you arrive at work. You rest your palms on the keyboard to begin typing your password, and recoil in pain from the sudden cold of the metal sucking the heat from your skin.

How do you quickly warm up a laptop? Make it do a lot of work.

Here’s a one-line, built-in command that will peg your CPU to 100%:

Run that from a Terminal, and don’t forget about it heh. What the command does is repeatedly send the word yes over and over to the null device, using 100% CPU.

If you want to stress your Mac more quickly and get your CPU hotter, try the stress utility:

brew install stress
stress -c 6 -m 2 -t 300

This will start 6 threads that each peg your CPU to 100% and 2 thread that do memory malloc/free. It has a 300-second timeout (5 mins) in case you walk away from your computer so it doesn’t overheat.

Bonus points, you can add an alias to your ~/.bash-profile to automate these options:

alias warm='stress -c 6 -m 2 -t 300'

fred: bash$ warm
stress: info: [65121] dispatching hogs: 6 cpu, 0 io, 2 vm, 0 hdd

Happy winter!