The CPU’s operate on a scale kilohertz (KHz) to megahertz (MHz) to gigahertz (GHz), a thousand times per second, million times per second, and a billion times per second respectively.I'm not so sure about these ECU's processing, "millions of things per second". If my 2015 Jeep Grand Cherokee sits for several days to a week without being run, it sometimes will start without the screen booting up. Others on the various Jeep forums have had this issue as well.
This can be remedied by pressing the "START" button twice with my foot off the brake pedal. This allows for all of this electronic crap, (including the screen), to boot up without starting the engine. (The same as turning the key to "ON", waiting, then cranking the engine).
(It also allows the fuel pump to prime the engine). Then, after a few seconds I depress the brake, press it again, and everything starts and boots up normally without issues.
The ECU doesn’t have to load a graphic interface, audio codecs, security software, communicate with various other ancillary CANBUS modules, and load up touch screen drivers like the radio has too.