info-mac@uw-beaver (info-mac) (07/26/84)
From: olson@harvard.ARPA (Eric Olson) The Mac has two directories: one collected together in a desktop file, and one distibuted on the diskette, in each file's header. If the desktop file gets destroyed somehow (which is catastrophic on most machines), the Mac MAY sense this and rebuild. Folders are lost because they are stored only in the directory in the desktop file. If the Mac doesn't sense it, system errors may occur subsequently and may sometimes be cured by the command-option reset, which forces rebuilding the desktop directory from the distributed directory. None of this is kept in memory when the Mac is turned off; it is carefully kept in the directory. The Mac does remember the bell volume across powerups, as well as "most control panel settings (manual p. 97). -Eric.
info-mac@uw-beaver (info-mac) (07/26/84)
From: Mark H. Nodine <mnodine@BBNH.ARPA> From what I can tell, you are partly right and partly wrong about what gets kept when the Mac is turned off. The clock is not kept in memory (otherwise it would not continue to advance when the power is turned off), but rather is kept by a single timer chip (which also has an alarm) and which is powered by a battery. The Mac documentation implies that this battery will need to be replaced every couple of years. The information about the desktop is not kept when the Mac is turned off. All of this probably comes from some "default" arrangement of the desktop when it reconstructs the disk. If the desktop information were, in fact, kept by the Mac, then you would not lose all of your folder information, since that is essentially an optical illusion created by the desk manager. Of some interest, however, is that there are 20 bytes of non-volatile RAM in the Macintosh. I don't know of any documentation for them other than what is in the comments for sysequ.h, but here is what I glean (if anybody has any further information, please let me know): Byte 1 validation field (? is this like a serial number?) Byte 2-4 odometer (I guess you can figure out how much you have been using your Mac) Byte 5-8 port configurations Byte 9-12 alarm time Byte 13-14 default font id Byte 15 bit 0-3 keyboard repeat threshold (in 4/60ths) bit 4-7 keyboard repeat rates (in 2/60ths) Byte 16 print stuff (This may be how MacWrite keeps track of the information about your printer, such as cut sheet, which it seems to remember without fail regardless of what disk you run from) Byte 17 bit 5-7 volume control Byte 18 bit 0-3 double time (in 4/60ths) bit 4-7 caret blink time (in 4/60ths) Byte 19 bit 0 english/metric bit 3-7 country code (!) Byte 20 bit 0 paranoia level (?) bit 1 mouse scaling (must be linear vs. velocity) bit 2 keyclick bit 3 boot disk (? This could be useful.) bit 4-5 menu flash (?) bit 6-7 help level (?) That's all the info and guesses I have. Enjoy, Mark