Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!nrl-cmf!ukma!tut.cis.ohio-state.edu!rutgers!att!alberta!ubc-cs!van-bc!root
From: lphillips@lpami.wimsey.bc.ca (Larry Phillips)
Newsgroups: comp.sys.amiga
Subject: Re: Crashing all the way to Kickstart
Message-ID: <2224@van-bc.UUCP>
Date: 11 Feb 89 17:11:03 GMT
Sender: root@van-bc.UUCP
Lines: 38

In <716@jhunix.HCF.JHU.EDU>, ins_adjb@jhunix.HCF.JHU.EDU (Daniel Jay Barrett) writes:
>	I was the original poster of this problem.  Larry, your explanation
>make sense... but why would the Amiga crash all the way to Kickstart
>only *sometimes*?  With a corrupted Kickstart disk, I would think that every
>crash would go back to Kickstart.

>	I also have a modified Kickstart (with KFont3 replacement font),
>but I have had this problem even with a totally unmodified Kickstart disk.

Right. Well, let's look at what's common. A good place to start might be WCS,
the memory that the KS loads into. One or more bad bits could easily cause the
same problem. memory, unfortunately, does not always fail solid, but can have a
'weak bit'. Even one bit in the checksummed area of WCS could cause a reset
back to KS.

Here's a little experiment you might want to try.  Write a program that
checksums WCS ($F80000 - $FFFFFF).  The algorithm need not be the same as the
one the reset routine uses. For best results, you might want to do it in both
words and longwords, in case you have multiple bit failures that cause one of
the methods to 'come out right'. Write it to simply print the result to the
screen, then when you have the values, modify it to check for these values and
tell lyou 'OK' or 'Whoops'.

Before each test of a program you are running, run your checksum program. The
two easiest ways to do this are either using an entry in 'make' to run it, or
by launching your program via a script which first runs the checksum. Writing
it in assembler will make it acceptably fast.

-larry

--
Frisbeetarianism: The belief that when you die, your soul goes up on
                  the roof and gets stuck.
+----------------------------------------------------------------------+ 
|   //   Larry Phillips                                                |
| \X/    lphillips@lpami.wimsey.bc.ca or uunet!van-bc!lpami!lphillips  |
|        COMPUSERVE: 76703,4322                                        |
+----------------------------------------------------------------------+