Re: What part of a fried GS is salvageable?

[nparker@inferno.uoregon.edu (Neil Parker)]

In article <19980222051800.AAA14997@ladder03.news.aol.com>,
Supertimer <supertimer@aol.com> wrote:
>[...munch, crunch, chomp, yum yum...]
>I'll do as you suggested and keep the parts around.  Do you know if there
>is any harm in plugging the removable IC's in a working GS board to see
>if they still work?  Thank you for your help!

That probably depends on the chip.  In some cases, bad chips can propagate,
as I found out the hard way a few years ago.  Gather 'round, kiddies, while
Uncle Neil tells you the blood-chilling story of the Night of Damnation...

It all started one day when I noticed some strange behavior in the Finder--
things were crashing a bit more often than usual, and icons were turning
into snow.  Rebooting would restore everything to normal, but after a while
the snow would be back.  At the time my system had few inits, DAs, and the
like other than the ones from the system disk, so I doubted it was an init
conflict.  Finally I fired up the Appleworks GS memory tester and let it
run for a while.

Sure enough--bad memory.  So I took out my Apple 1-meg card, and brought it
in to a friend who repairs Apple II and Mac equipment.  That's when the
real trouble began.

We plugged the card into my friend's GS, and he ran his diagnostic
software, and we verified that there was indeed a bad memory chip.  But
which chip needed to be replaced?  My friend had another card from a
different manufacturer that came with diagnostic software that could pin
down the exact socket of a bad memory chip, so we started pulling chips off
my board and plugging them into his board.  That turned out to be
remarkably ineffective--the diagnostic software saw problems with my chip
sure enough, but it also reported that my friend's known-good chips were
bad.  So we took my chips out and put his back in, and it still reported
his chips as bad.  The Appleworks GS memory tester agreed--his known-good
chips had suddenly failed.

So we tried it the other way--we found some more known-good chips and tried
plugging them into my board.  The Appleworks GS memory tester found that
these too had suddenly gone bad.

By now both of us were beginning to suspect the truth...no only did I have
bad memory chips, but the error was contagious--any other chip plugged into
the same row in the same card as a bad chip also went bad.  And not only
that, but the newly-killed memory chip acquired the ability to kill other
chips in exactly the same fashion.

All told, we managed to ruin an entire container of previously-working RAM
chips that evening.  I had to start over with a completely fresh supply of
RAM chips, and a new board as well.

             - Neil Parker
-- 
Neil Parker, nparker@inferno.uoregon.edu, nparker@axis.llx.com,
http://axis.llx.com/~nparker/     (Note new addresses and home page!)

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