This article originally appeared in TidBITS on 1992-01-27 at 12:00 p.m.
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Zapping the PRAM

by Eric Apgar, Robert Hess and Adam C. Engst

With the exception of date and time, all system-wide preferences are reset to default values by zapping the Parameter RAM (PRAM). If you wish to zap the PRAM, hold down shift-command-option and choose the Control Panel in System 6. In System 7 hold down command-option-p-r (Be sure Caps Lock is off!) at boot time, and then let go at the second startup chime. The Macintosh will restart shortly after displaying the "Welcome to Macintosh" screen, which indicates that PRAM has been reset. The date and time settings are actually read out of PRAM before it is zapped, then written back in afterwards. Note that if a Macintosh's battery is drained, the date and time will reset to the default value (12:00 am, January 1, 1904) after each startup.

What's in the PRAM? -- If you have ever wondered what information is stored in the parameter RAM, this list should answer your questions and help you in figuring out when zapping the PRAM might be useful.

default: 24-bit Addressing
default: mid-range on the slider
default: black
default: middle setting
default: 3 times
default: 12:00 am, January 1, 1904
default for repeat: one away from Fast
default for delay: one away from Long
default: 16K
default: primary monitor only, set to Black & White
default for tracking: Very Slow
default for double-click: Middle setting
default: Simple Beep, even though it is not highlighted
default: none set, will use standard volume search method
default: AppleTalk is active.
default: Built-in LocalTalk port is selected
default: Faster is selected
default: Faster is selected
default: RAM disk is off, size is set to 192K.