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From: hojo@cbnewsb.cb.att.com (HC Johnson)
Newsgroups: comp.sys.atari.st
Subject: Re: Help! Hot memory?
Summary: You probably have bad bits
Message-ID: <1991Mar14.173342.2902@cbfsb.att.com>
Date: 14 Mar 91 17:33:42 GMT
References: <5116@mindlink.UUCP>
Sender: news@cbfsb.att.com
Organization: AT&T Bell Laboratories
Lines: 28

In article <5116@mindlink.UUCP>, Bill_Moore@mindlink.UUCP (Bill Moore) writes:
> I have an older ST (purchased in 1986) with an easieST memory expansion board
> installed with 2mb of memory.  Recently it has begun to lock up with narrow
> vertical lines on the screen and eleven bombs. This happens when the machine
> has been on for at least 1 1/2 hrs.  If I am able to reboot I have only 1/2 mb
> of memory available.  I had the connections to the expansion board soldered,
> and that has improved the problem -- it happens less often and the machine can
> be on longer -- but it still happens.  Any ideas??  Suggestions??  Did this
> ever happen to anybody else out there?  Thanks in advance -- a lot!!

You probably have 1 or more bad bits in the addon memory.
Remember, 1 bit is in each of the 16 chips.

When the bit goes bad, so goes the programs running in that memory; and you
lock up.  On reboot, TOS does a memory existence test to size the machine.
Your memory does not read back what TOS wrote, so the memory is truncated
at .5Meg.

This happened to me.  I wrote a simple C program to write/read back memory
starting at 0x8000 and soon found a bit being dropped. (write 0xffff to see
if a bit comes back 0, then write 0x0000 to see if a bit comes back 1).
In my case 1 bit was usually a 1. (it was floating).  I replaced the
corresponding  chip and all was well.

Howard Johnson
ATT BELL LABS
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hcj@lzsc.att.com