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Reasons to Add More RAM to Mac Snow Leopard

Of all the possible upgrades that you can make to your Macintosh, 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, as shown in this figure. 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.

    The mysterious beauty of virtual memory — but it still doesn’t beat real RAM!
    The mysterious beauty of virtual memory — but it still doesn’t beat real RAM!

At first, virtual memory sounds like absolute bliss, and it does indeed allow your Macintosh to do things that would otherwise be impossible, such as running an application that requires 2GB of RAM in just 1GB of actual physical RAM. However, here come the caveats:

  • Virtual memory is as slow as molasses in December. Even today’s fastest hard drive is many, many times slower than real silicon, 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 128MB of RAM, you’re having flashbacks right now. Whenever your Macintosh is using virtual memory, your hard drive remains almost constantly active. (Hardware types call this phenomenon thrashing.) 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 Mac has to spend part of its quality time shuttling data to and from the hard drive, which robs your computer of processing power.

    The less Mac OS X needs to use virtual memory, the better. To put it another way, 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, 128MB of RAM was a quite comfortable figure for most folks, but all of today’s Macs can accept at least a whopping 4GB (that’s short for gigabyte, or 1,024 megabytes) of system RAM. (At the extreme end of the scale, the King Kahuna — Apple’s latest Mac Pro — can now accommodate an unbelievable 32 gigabytes of RAM!)

If you’ll be keeping your current Macintosh for a few years more, install as much memory as you can afford — you’ll thank yourself every time Mac OS X Snow Leopard boots.

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