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From: wtm@neoucom.UUCP
Newsgroups: comp.sys.ibm.pc
Subject: Re: Date not advancing at midnight on my clone
Message-ID: <391@neoucom.UUCP>
Date: Mon, 2-Mar-87 09:51:33 EST
Article-I.D.: neoucom.391
Posted: Mon Mar  2 09:51:33 1987
Date-Received: Tue, 3-Mar-87 22:20:14 EST
References: <4728@shemp.ucla-cs.UCLA.EDU>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 24
Summary: The bug is in DOS


The date roll-over problem is a well-known bug in DOS.  Virtually
all flavors of MS and pc DOS have it.  It's been a while since I
looked the code over, but it If I remember right, the timer tick
interrupt sets a date rollover flag at midnight.  Normally, the
keyboard interrupt would call code that would handle the flag and
make sure that the date got changed.  The problem arises if the
first operation after midnight is disk I/O, then the state of the
rollover flag is lost, and the date gets stuck.

Note that you are still gyped if you leave your machine on, but
idle over the weekend, becuase the flag will only be set once, and
the computer won't be aware that there has been more than 24 hours
elapse since the flag was last checked.  Basically dumb, but that's
what you get from something designed for the business world that
only has to be right from 8:00 to 17:00 (grin).

  --Bill

Bill Mayhew
Division of Basic Medical Sciences
Northeastern Ohio Universities' College of Med.
Rootstown, OH  44272  USA    phone:  216-325-2511
(wtm@neoucom.UUCP   ...!cbatt!neoucom!wtm)