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From: john@hpcvlo.HP.COM (John Eaton)
Newsgroups: sci.electronics
Subject: Re: Battery-Backed Clock Goes Back
Message-ID: <1090004@hpcvlo.HP.COM>
Date: Tue, 8-Sep-87 12:19:10 EDT
Article-I.D.: hpcvlo.1090004
Posted: Tue Sep  8 12:19:10 1987
Date-Received: Fri, 11-Sep-87 06:42:06 EDT
References: <8709032058.AA01589@hoser.berkeley.edu>
Organization: Hewlett-Packard Co., Corvallis, OR, USA
Lines: 24

>>>>>>>
>>
>>...that battery should last somewhere in the range of 10-30 years...
>>(="=)	bryce@hoser.berkeley.EDU -or- ucbvax!hoser!bryce
>
>I find this hard to believe.  Shelf life for Lithium batterys is about
>three years, and those are long life batteries.
----------
I find it hard to believe that anyone would bother to design a 30 yr clock
for a computer. Think of where you were 30 years ago and what computer you
were using then. Are you still using the same system? I didn't think so.
There are other parts of the computer that become obsolete long before the
battery gives out.

If the design goal is for the system not to lose time for 30 years then you
also have to consider the effect of crystal tolerance. Your standard 20ppm
clock crystal will be off by over 5 hours over the course of 30 years and this
will require user intervention anyway. 30 years is not as useful as it
sounds.



John Eaton
!hplabs!hp-pcd!john