On 4/13/2010 6:37 PM, Larry Blanchard wrote:
On Tue, 13 Apr 2010 15:54:58 -0500, Robert Bonomi wrote:

It took a while to establish cause-and-effect, because *nobody* was
willing to believe that that 'innocent little job" -- nothing more than
4 standard statements in the system control language -- could _possibly_
be the culprit. Until they ran it as the _only_ job in the system, and
watched the machine crash.

The entire job consisted of:
1) request a tape mount
2) copy a file from disk to the tape
3) rewind the tape
4) copy from the tape back to a new file.

The original Univac I had tape drives that maintained tension with
springs and pulleys rather than vacuum columns. Those drives, as well as
the vacuum column model that replaced them on Univac II, could read both
forwards and backwards. There were 10 drives.

One of the programmers (no, not me) wrote a program that issued a write
command, followed by a read backwards, followed by a skip a block. That
sequence apparently exceeded the response of the strings and pulleys and
they wound up in a heap at the bottom of the drive.

The resident (yep, 24 hours a day) CEs wouldn't believe him when he
described the problem. So he wrote a little program to demonstrate the
problem, called in the CEs, and ran the program, dumping *all 10* tape
drives. He wasn't very popular with the CEs after that, but when he told
them he had a problem, they listened :-).

I sometimes think all us old computer nerds should start a website and
record all these stories before we all die and the stories are lost.

The IBM-1130 used a 1-card IPL program that was normally used to fetch a
resident supervisor image from disk, and I kept a stack of 'em on the
console for convenience...

I also made a hobby of writing 1-card boot programs to do things like
making a copy of the supervisor image in the last of three spare
cylinders on the disk, restoring from same, copying card decks,
gang-punching control cards... and a little program that would seek past
the innermost track to nudge a little rubber bumper against the drive
hub - repeatedly - to make a really nasty buzzing sound.

Not exactly sure how it happened to be on top of the stack of boot cards
when our friendly FE came in to do scheduled PM. He grabbed a
"joybuzzer" card to boot up the machine, and totally freaked out a
second time when told "It does that sometimes".

He did take it more in stride the time he booted up the machine and the
printer wasted a page to inform him that "Sometimes I feel like a
motherless child"...

He did not take it so well when someone (caugh) patched the resident
supervisor idle loop to do a WAIT when the machine was waiting for work
(could be anything from an empty card reader hopper to the interval
between card columns while actually reading a card). Seems like the
runtime meter (from which IBM billed the school) stopped when the CPU
was in a wait state. The school's billings had suddenly dropped
mysteriously by 90% and the branch office manager was (very) upset about
lost revenue. The FE really was friendly - he negotiated a "Wink, wink,
nod, nod, promise not to share this with other customers and you can
keep the 90% discount" agreement.

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/