Reasons to Add More RAM to Your MacBook - dummies

Reasons to Add More RAM to Your MacBook

By Mark L. Chambers

Of all the possible upgrades that you can make to your MacBook Pro, adding more random access memory (RAM) is the single most cost-effective method of improving the performance of Mac OS X. (In fact, your machine will likely run faster with more memory than a reasonably faster processor!) Here is exactly what Mac OS X uses available RAM for:

  • Applications: Naturally, Mac OS X needs system RAM to run the applications that you launch. The more memory in your machine, the larger the applications that you can open and the faster they’ll run.

  • Overhead: This includes the operating system itself, as well as various and sundry buffers and memory areas devoted for temporary work. As you would guess, the more memory here, the merrier.

  • Virtual memory: Virtual memory allows Mac OS X to use empty hard drive space as temporary system memory. Data is written to your hard drive instead of being stored in RAM, and then it’s erased when it’s no longer needed. This is a neat trick that’s also used by Windows and Linux. Virtual memory works automatically within Mac OS X.


At first, virtual memory sounds like absolute bliss, and it does indeed allow your MacBook to do things that would otherwise be impossible, such as running an application that requires 4GB of RAM in just 2GB of actual physical RAM. However, here come the caveats:

  • Virtual memory is as slow as molasses in December. Today’s fastest hard drive is many, many times slower than real silicon (and even solid-state hard drives, which actually use memory chips as well, are still much slower than your Mac’s system RAM), so any use of virtual memory instead RAM slows down Mac OS X significantly.

  • Virtual memory abuses your hard drive. If you’ve ever run Photoshop on a Windows PC with 1GB of RAM, you’re having flashbacks right now. Whenever your MacBook is using virtual memory, your hard drive remains almost constantly active.

    (Hardware types, like myself, call this phenomenon thrashing because we know what’s happening inside that poor hard drive.) Over time, running any computer with insufficient RAM and behemoth applications will result in a significant increase in hard drive wear and tear.

  • Virtual memory costs you processing power. With sufficient RAM, Mac OS X gleefully runs as efficiently as it can. When virtual memory kicks in, however, your MacBook has to spend part of its quality time shuttling data to and from the hard drive, which robs your computer of processing power.

Physical memory (meaning memory modules) is always a better choice than virtual memory. This is why power users and techno-types crave as much system memory as possible.

A little over five years ago, 256MB of RAM was a quite comfortable figure for most folks, but today’s MacBook Pro models can accept a whopping 8GB (that’s short for gigabyte, or 1,024 megabytes) of system RAM. (The MacBook Air comes from Apple preconfigured with either 2GB or 4GB of RAM. The Air is a sealed unit, so the RAM can’t be expanded.)

If you’ll be keeping your current MacBook for a few years more, order it with as much memory as you can afford (or if possible, install more).