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From: info-mac@uw-beaver (info-mac)
Newsgroups: fa.info-mac
Subject: Re: Rebooting options; what's kept around?
Message-ID: <1332@uw-beaver>
Date: Thu, 26-Jul-84 13:36:36 EDT
Article-I.D.: uw-beaver>.1332
Posted: Thu Jul 26 13:36:36 1984
Date-Received: Fri, 27-Jul-84 07:29:58 EDT
Sender: daemon@uw-beave
Organization: U of Washington Computer Science
Lines: 56

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