Parameter RAM
Parameter RAM, or PRAM as it is commonly called, holds certain pieces of information where it is useful for quick acces, particularly between reboots. Apple KnowledgeBase article 86194 has a valuable description of what kinds of information are stored in PRAM.
From the article, Mac OS X stores only the following:
- Time zone setting
- Startup volume choice
- Speaker volume
- Recent kernel panic information, if any
- DVD region setting
"Mac OS classic" versions also store:
- Network settings, especially for AppleTalk
- Monitor/display settings
Adobe Knowledgebase document 315344 also provides general PRAM information (courtesy of MacFixIt). It indicates that the following are stored in PRAM, presumably for classic Mac OS:
- validity status of the clock chip
- clock settings (alarm setting, time, date)
- node ID hint for a modem port (9600 baud, 8 data bits, 2 stop bits, no parity) and printer port
- modem port configuration stop bits
- printer port configuration and connection
- printer connection
- monitor colors
- application font number minus 1
- auto-key threshold and rate
- speaker volume
- double-click time
- caret-blink time
- menu blink
- mouse scaling
- preferred system start-up disk
- network setting (network defaults to LocalTalk)
Of note, the Adobe document states, "The only proven time resetting the PRAM may be of benefit is if your Macintosh computer fails to start up under any circumstances." Our experiences tend to back this up; zapping or resetting the PRAM appears to be a low-probability fix for problems, unless you are having problems starting up at all, or displaying video at startup.
