What really happens is in fact very similar to what happens in the javascript event loop. The processor processes instructions one after another, synchronously

What really happens is in fact very similar to what happens in the javascript event loop. The processor processes instructions one after another, synchronously, but whenever he has to use something external he makes the call and continues his normal life until the interruption triggers. The javascript event loop consists in placing function calls in stack and using WEB api calls asynchronously.