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From: info-mac@uw-beaver (info-mac)
Newsgroups: fa.info-mac
Subject: Re: re..bad ext.disks
Message-ID: <2338@uw-beaver>
Date: Tue, 27-Nov-84 05:09:59 EST
Article-I.D.: uw-beave.2338
Posted: Tue Nov 27 05:09:59 1984
Date-Received: Wed, 28-Nov-84 04:14:51 EST
Sender: root@uw-beave
Organization: U of Washington Computer Science
Lines: 65

From: <ihnp4!hplabs!bragvax!kari@uw-beaver.arpa>
I recently pushed the programmer's RESET switch while the Mac was
booting from the internal drive, for the first and definitely the last
time. (I thought: Surely the bright people at Apple have designed the
Mac to handle this gracefully... Not so.)
Friends of mine claim they push the switch any time they please and
nothing bad happens to THEM. I choose not to believe them from now on.

The results were pretty bad:

1. Trying to boot from the same disk gave a Sad Mac Icon. Trying to boot
   from another disk failed. Turned the machine off, tried again,
   failed.  After a while I managed to boot from a system disk.

2. The disk I was booting from when I hit the reset button could not be
   read. It could not even be erased or reformatted or zeroed. Bulking
   it might work, but I have no access to a bulk eraser.  In the next
   hour I had severe problems with the Mac in that I sometimes could not
   read a disk in the internal drive, sometimes not in the external,
   sometimes not in either. I ran disk verifies and disks would fail
   with various rates. I believed I began to see a pattern to the
   failures:

3. (Theory): The internal drive head had gotten semi-permanently
   magnetized when I hit the reset button. It was corrupting my disks.
   This theory gets supported by the fact that the some of the errors
   were soft, failing only occasionally, (The recording had partly faded
   away because the disk was read with a magnetized head) and by the
   fact that several disks were damaged after I had pushed the button
   ONCE.

4. I created two new (identical) disks on another Mac I have access to
   (the following day at work), containing a system folder and the disk
   utility program.  I then ran disk verifys on both drives. The
   internal drive would eventually start failing. I then zeroed the
   internal drive disk and then copied new contents from the other one.
   (At least with analog taperecorders, if you cannot deflux them,
   record on them. They contain special circuitry to deflux the heads
   when the recording bias oscillator is turned off. I just "massaged
   the head" by using it a lot.)

5. After half an hour I felt confident that the disks did not get any
   worse by reading them in the internal drive. I have not had any
   problems since then.

6. Two days later I did an inventory of all the disks I had touched
   while I had problems. Six disks out of about 15 I had been reading
   from did not verify correctly. I refused to use ANY file from any
   disk that did not verify correctly. I did not lose any work since I
   have two backups for everything (since I have one Mac at work also).

7. The above procedures were not conducted in any scientific manner.
   I did not keep notes. Things may have happened slightly differently.
   All I know is that my Mac now works, I have one disk that cannot be
   formatted no matter what I do, and one that fails marginally (every
   other verify or so). I have never had any problems with my Mac
   before. I have no problems now.

If anyone else has had a similar experience, I would be interested in a
summary. 

/Kari

Kari Dubbelman, BRAG Systems Inc., San Mateo CA  (415) 342-3963 X218
(...decvax!ucbvax!hplabs!bragvax!kari)