Computer Memory: Delivering Data at Top Speed

Without memory, your computer would be useless. Read on to explore how it retrieves all the things it knows.

If you tried to locate a singular “brain” inside your computer, you'd probably wind up at the central processing unit (CPU). The CPU runs programs and accesses various memory banks, moving information where it needs to go. Some of a computer’s memory banks keep information stored permanently, the hard disk being foremost among them. But much of your CPU’s daily workload takes place within the computer's temporary memory banks, particularly its random-access memory (RAM) and its cache.

When a computer is turned on, the CPU opens stored programs from the permanent hard disk, but it runs them in temporary RAM space. Running a program includes processing every keystroke or mouse movement you make—which adds up to a lot of info that you'll never need again, so RAM purges it all once the computer is turned off.

That’s one thing that allows RAM to be hundreds of times faster than a hard disk. Another is the random part of its name. This means simply that its data can be accessed in any order via integrated circuits, every element of which is electrically interconnected with every other element. By contrast, finding something on a hard disk is more like finding something on a VHS tape: you can view any scene you want, eventually, but first you’ll have to fast-forward through all the mushy kissing scenes and boring talking scenes that come before it.

The cache is similar, but it’s even smaller and faster. It holds copies of files you’ve recently used; when you try to access something, the CPU will first check to see if it can make the short, fast trip to the cache to retrieve it rather than going all the way to the RAM or the hard disk. When you’re using the internet, your browser also keeps a cache. If you return to a page you’ve already visited, it will fetch you a copy from the cache rather than requesting it again from the server where it’s hosted.