Resetting Parameter RAM (PRAM) deleted my RAM disk and its contents. Why?

If you are using a RAM disk, and Parameter Ram (PRAM) is reset, by simultaneously holding down the Command-Option-P-R keys at the initial startup chime, the settings in the Memory control panel revert to their factory defaults.

The default setting for a RAM disk in the Memory control panel is "off". As a result, any contents on a previously active RAM disk are lost when the PRAM is reset.

This happens regardless of whether or not the RAM disk is the startup disk. The presence of the Assistant Toolbox extension (on a Powerbook computer) does not prevent this data loss. You should back up all important items from a RAM disk to another disk before resetting the PRAM.

Note: Restarting the computer does not purge the contents of the RAM disk. Selecting Shut Down from the Special menu or powering the computer off using the power switch erases the contents of the RAM disk, unless the Assistant Toolbox extension for PowerBook computers, or a similar utility for other Macintosh computers is installed. If the computer is shut down in this manner, the contents of the RAM disk cannot be retrieved even if the computer is immediately restarted.

For additional RAM Disk information, see the following articles: