Re: re..bad ext.disks

[Info-Mac]

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From: info-mac@uw-beaver (info-mac)
Newsgroups: fa.info-mac
Subject: Re: re..bad ext.disks
Message-ID:
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:
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)