About This Macintosh...

The simplest way to tell how much free RAM your Mac currently has available can be found in the About This MacintoshÉ dialog.

To check the amount of RAM installed in your machine and the amount available to assign to an application, restart your machine and, before opening any other application, open the About dialog from the Apple menu:

Doing this after a restart and before opening any applications will tell you the maximum amount of memory available for your system settings, since it will check memory before the OS starts juggling memory requests from different applications.

This will bring up the About This Macintosh dialog (the exact contents will vary depending on which OS version you are running):

If you have never changed your Mac's memory settings, probably Virtual Memory is enabled:

Note that the figures shown in the About dialog are actually estimates by the OS and change quite frequently as you use the computer; don't be alarmed if they do not total correctly.

The total amount of memory available on the machine can be found in one of two places, depending on whether or not your are using Virtual memory:

• Virtual Memory disabled: total memory available = Built-in memory (in the top figure above, 352 MB).
• Virtual Memory enabled: total memory available = Virtual Memory (in the bottom figure above, 64 MB).
  Note that this the system is not using 64 MB of hard disk space as Virtual Memory; rather it is using the 32 MB built-in memory + 32 MB hard disk space = 64 MB total memory

Under OS 9, the available memory that can be assigned to applications is the Largest Unused Block, the 4th item in the list in the middle of the dialog (in the top figure above, app. 299.4 MB; in the bottom figure above, app. 47.4 MB).

Recommendation: Do NOT use Virtual memory unless your machine has only 32 or 64 MB of RAM. It will slow down your work unnecessarily. If you have 96 MB of RAM or above, you probably have more than enough free RAM for OS 9 and to assign Signalyze the optimal amount of 16 MB, with enough left over to run another application or two if you need to. (See the increasing available memory page for suggestions on how to upgrade your Mac's memory.)

Make sure you leave another 1 MB or so free for the OS to use as it needs. This will help prevent it from crashing when it is performing memory management-related tasks. In other words, make sure that the Largest Unused Block figure will always read at least 1 MB of free memory that is not assigned to any application.