10 Apr
2006
10 Apr
'06
11:28 a.m.
Hey, I was just skimming Knuth's Art of Computer Programming chapter
where he talks about external sorting. It occurred to me that doing a
massive external sort would be an impressive demo for someone viewing
a collection.
Does anyone here own enough 9-track magtape drives to do external
sorting and multi-tape merge operations? It would be cool to watch a
time-lapse film of the operation!
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10 Apr
10 Apr
11:51 a.m.
Richard wrote:
Hey, I was just skimming Knuth's Art of Computer
Programming chapter
where he talks about external sorting.
tape sorts make IBM 3420's make the strangest noises you might ever hope
to hear
out of a drive. Most of the action is not visible, but is in very high
frequency vibrations
in the vacuum columns, and some unusual motion in the tape loops in the
columns.
The 3420s can do 200ips forward or reverse reading, which suit them
quite well
for sorting. The tape sorts were faster than the dasd sorts at the time
I saw one
run in the late 80's on systems with 3380 drives, for large data sets.
There was a 3420 and 3803 for sale in an Ebay auction mentioned in another
thread. There is a lot of IBM stuff for sale from vendor "retrosoft" if
anyone
wants to look.
Jim
11:54 p.m.
On 4/10/2006 at 11:51 AM jim stephens wrote:
tape sorts make IBM 3420's make the strangest
noises you might ever hope
to hear out of a drive. Most of the action is not visible, but is in very
high
frequency vibrations in the vacuum columns, and some
unusual motion in the
tape
loops in the columns.
Sorting (and its cousin, merging) used to be a big deal in the data
processing world. Many hours were spent working with oscillating or
polyphase merge sorts. I remember when I was told that I could use DISK to
sort my data (we had a large roomfull of CDC 844s). My reaction was "wow,
with random access to any point a file, I can really make a sort fly!"
When it got down to paper, however, it turned out that the old methods that
used tape also worked very well on disk. I remember how disappointed I
was--sort of like being told that there was no Santa Claus.
For those of you unaccustomed to tape sorts and wondering how that could
possibly be; remember that we used multiple tape drives and while a tape
might be rewinding, data was still being written and read to other tapes.
You might think that you'd save a lot of time by not having to rewind a
disk, but it really doesn't matter.
Cheers,
Chuck
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