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Path: utzoo!utgpu!water!watmath!clyde!rutgers!husc6!seismo!vrdxhq!bms-at!stuart
From: stuart@bms-at.UUCP
Newsgroups: comp.misc
Subject: Re: What the world needs now [ is an exploding computer ]
Message-ID: <402@bms-at.UUCP>
Date: Thu, 28-May-87 15:02:14 EDT
Article-I.D.: bms-at.402
Posted: Thu May 28 15:02:14 1987
Date-Received: Sat, 30-May-87 05:32:02 EDT
References: <12067@topaz.rutgers.edu> <910@killer.UUCP> <15@gordon.UUCP> <2725@phri.UUCP>
Organization: Business Management Systems, Inc., Fairfax, VA
Lines: 19
Keywords: Originally from a friend
Summary: I did it!


I inadvertently wrote a BASIC program on an HP2000 at George Mason University
that blew up the disk drive.  It was an 8 player real time space war game.
The problem was that all interprocess communication had to take place via
disk.  I used the documented LOCK function for serialization.  It seems that
this function loaded a special OS overlay whenever invoked and reloaded 
the file I/O overlay directly afterward.  With 8 programs doing this
as fast as possible, the disk would die.

The problem was solved by using an undocumented feature of the scheduler.
A process was always assigned 1 sec of CPU following completion of a wait
for terminal I/O.  This allowed serialization with careful coding while
not using the LOCK overlay.

BTW, an IBM PC program can blow up the monitor and video cards by programming
nasty parameters into the video controller chip.

-- 
Stuart D. Gathman	<..!seismo!dgis!bms-at!stuart>