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From: sdh@joevax.UUCP (The Doctor)
Newsgroups: net.micro.apple
Subject: Re: ][+ w/munged memory
Message-ID: <320@joevax.UUCP>
Date: Thu, 16-Oct-86 10:22:44 EDT
Article-I.D.: joevax.320
Posted: Thu Oct 16 10:22:44 1986
Date-Received: Fri, 17-Oct-86 03:16:47 EDT
References: <861015190558.956605@HI-MULTICS.ARPA>
Organization: Bell Communications Research Inc., Morristown, NJ
Lines: 39

> My ][+ has the following hard memory failure:  at locations 8000 and
> above, the monitor commands
> 
> *8000:  00 00 00 00 00
> 
> *8000.8004
> 
> results in a display of
> 
> 40 40 40 40 40
>

This means that the seventh bit is being set all the time.  One of your
ram chips is bad.   Here's one way to fix the problem:  run a ram test on
it.  If your local Apple dealer wants to keep you as a customer, they should
be more than willing to give you a copy of the apple approved ram test
program, or borrow an Integer Basic firmare card, since it contains a ram
test on board.  Either should tell you which 4116 is bad.  Your other
alternative:  go to Radio Shack and buy 1 4116 ram chip.  Locate the bank
of 4116's on the motherboard.  The row closest to the slots will contain
the last 16k of ram --that's where your problem is.  I don't know which of
the chips is the bad one, but just use the process of elimination to find
the bad chip.  Most likely, it will be either the 2nd from the left or the
2nd from the right in that row.   NOTE: always make sure the power is off
before you swap chips, and beware of static elctricity.  You may want to
spread aluminium foil on the table under your apple, as that will help deter
static charges.

A side note, there are times when a bad ram chip will work just fine when
swapped with another chip.  I've done this before: found a bad chip, and
swapped it with its neighbor, and removed the problem, but for piece of mind,
you should use a new chip as the replacement.

The reaseon why you can't boot your disk is that DOS is loaded in the last
16k of ram.  Since your ram failure is there, every byte of dos is getting
OR'ed with $40, thus making DOS invalid.

Steve Hawley
joevax!sdh