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Apple has traditionally not been over-generous with the amount of RAM that they ship with their machines, especially lower-priced models. Even today, with RAM prices plumbing historic lows, the base iBook comes with a paltry 64 MB of RAM, which is barely adequate for using Mac OS 9.x, and totally inadequate for OS X.

A workaround built into the Mac OS is something called Virtual Memory, which allows you to commandeer a chunk of space on your hard drive to act as ersatz RAM. All new or Macs come with pretty big hard drives, so making this allocation is usually no hardship in terms of hard drive room.

However, Virtual Memory should not be considered an adequate substitute for real RAM, since the time lag involved in retrieving information stored on a hard drive is much longer than accessing data from RAM modules plugged into the motherboard. Virtual Memory is a temporary crutch rather than a permanent solution for working memory.

However, the Mac OS installs with a maximum amount of virtual memory (your real RAM capacity plus 1 MB) enabled for a reason. It improves performance because applications launch faster with Virtual Memory turned on, since all of their code must be copied into RAM from hard drive, and programs also use substantially less RAM when Virtual Memory is enabled. For example, the preferred memory setting for Tex Edit Plus with Virtual Memory turned on is 1,024k. Without Virtual Memory enabled, the program wants 1,483k. Adobe PhotoShop 3 specifies a preferred setting of 8,192k with VM enabled. Without Virtual Memory, it needs 13,441k. You can check the relative memory requirements of your applications by clicking on the application icon, and selecting Get Info from the File Menu. Use the pull-down menu in the Get Info window to select Memory.

If you have an adequate amount of real RAM installed (and there's never been a better time than now to stock up), then you should probably keep Virtual Memory turned on set at the minimum 1 MB more than your actual RAM capacity. Higher settings should read be reserved for emergencies.

To set Virtual Memory, open the Memory Control Panel from the Control Panels submenu in the Apple Menu. You will see buttons for turning Virtual Memory on and off, as well as a pull down menu that lets you select the volume or partition that will be used for Virtual Memory storage. If you have just one, non-partitioned hard drive, this is a default setting. There is also a field with up and down arrows that allow you to increase or decrease the amount of memory available.

As noted, in most instances he should set this to a figure 1 MB higher than the amount of real RAM you have installed. For example, if you have 128 MB of RAM, said Virtual Memory at 129 MB.

Once you have entered the desired settings, close the Memory Control Panel, and restart your Mac for them to take effect.