Unless you have a valid reason to do this, you’re better off not randomly running “yes”, since it obviously causes performance issues until it stops running.įor some assistance, the video below demonstrates the entire process from start to finish:įor those wondering, this works in all versions of Mac OS X and even linux as well, so you can stress test any Mac ever made this way. If not, there’s probably a typo in there somewhere. You’ll also see all instances of “yes” drop from the process list in Activity Monitor. When finished, in the same terminal window type “killall yes” into the command line to kill all instances of the yes command. You’ll quickly discover in Activity Monitor or top that the processor is getting hit hard. Yes > /dev/null & yes > /dev/null & yes > /dev/null & yes > /dev/null &

Either repeat the process by hitting up arrow and return to run another several instances, or throw a group onto a single line like so:

That sends one instance of ‘yes’ into the background, but to load up the CPU you’ll want to have more than one running. When ready to stress test the Mac, type the following command:

To begin, launch Terminal, and you may want to watch the UI-based task manager Activity Monitor so you can easily observe the CPU load and system resources. This means if you have a dual core Mac with a hyperthreaded processor, you’ll need to have at least four different instances of “yes” running to put full load onto the CPU. Generally speaking, each instances of “yes” will max out a single thread on a single CPU core.

To max out the Mac CPU we’ll use the command line tool called “yes”, which basically does nothing except repeat the word “yes” at such speed that it consumes all available processor resources.

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