[OT] More tape drive stories

[Jon maddog Hall]

gaf at blu.org said:
> First, you had to hold the reel on the hub until the hub locked (which the
> window was closing). 

Those windows over the tape reels were really important, however.  I remember when
one reel was rewinding and it was going so fast that the stresses caused the
plastic reel to disintegrate.  Small pieces of very sharp plastic went flying
all around inside that tape cabinet.  Any operator in that isle of tape drives (yes
we had isles of tape drives...several isles) would have been severely cut.

Another, earlier tape drive had no "take-up" reel.  The tape just fell into the bottom
of the cabinet in a pile, and when the tape rewound, it just pulled it back up.
It was actually amazing how many times it worked correctly......you might imagine
what happened when it did not work correctly.

My favorite tape, for many reasons, was the Link Tape, often called "DEC TAPE".
A small (about four inches) reel of tape, it was low enough cost and small enough
that a student could afford it and carry it around with them.  It had fixed blocks
of data with a directory at the front of the tape, and the blocks could be read going
forward and backward.  The tape also had the same information duplicated in two
tracks on the tape, in case one track was mutilated.  Since the tape was fixed block,
when you read the directory to find out where your file was, the computer could then
calculate how far into the tape your file was, go at high speed for some period of
time, stop, read a block and see if it was "close".  If not it re-calculated the time,
and went high-speed again.  If it was "close" it went at low speed (both forwards and
backwards) to get to the block you wanted.

If this sounds clunky, remember that our other main format was paper tape read in
from an ASR-33 teletype.  You really don't want to go there....it often took
HOURS for one turn-around of your program, with most of that time reading in paper
tapes.  DEC TAPE sped that process up considerably.

I first encountered DEC TAPE in 1969.  I was in the room at Digital in the late
1980s when DEC "retired" the tape system.  The last customer had gone off their service
agreement, and the last operating system had dropped support.  The tape was "dead".
As I looked around the room, there was no one in the room other than me who was old
enough to have suffered through paper tape.  To them, the format was "just another
tape".  So I stood up and told them what DEC TAPE meant to me and a generation of
college students and professors, and asked for a moment of silence for the passing
of a great tape format, and they gave it to DEC TAPE.  Several years later this little
tirade of mine was published in a book about Digital's history, and appeared on a
little display at the computer museum....apparently someone was taking notes in the
back of the room.

Most of us have that first piece of computer equipment that we fondly (or not so
fondly) remember as the "breakthrough" for us....the Kim-1, the Commodore, etc.
DEC TAPE was certainly in that category for me.

Warmest regards,

maddog
-- 
Jon "maddog" Hall
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