Operating old Mainframes was RE: Collection policy

From: Andy Holt <andyh_at_andyh-rayleigh.freeserve.co.uk>
Date: Sun May 25 04:41:00 2003

> > different today, how can people relate to this? While there are
> still a few
> > people who know how to make a horseshoe at a blacksmiths there will be
> > nobody who knows how to run the early mainframes in 50 years, things are
>
> Rubbish!. Are you seriously trying to tell me that these skills can't be
> learnt? ... <below

> -tony

Well, understanding these computers in an architecture sense is one thing* -
but operating and maintenance skills were usually verbally transmitted and
rarely permanently documented. They can probably be redeveloped with
experience but this experience is likely to be at the cost of media damage.
When I was a systems programmer on an ICT1905 (then a 1905E etc) I learned
some of the skills of the operators and even occasionally helped the
engineers (usually to diagnose processor problems with "odd" symptoms)

Things like:
 the skills of handling trays of punched cards so that the readers didn't
jam - and the practice of clearing the jams that did happen. (a 1600 cpm
reader can fling cards all over the place when it feels like it! - the 600
cpm reader was referred-to as "the mangler" by anyone who used it ... and
with good reason)
 loading magnetic tape drives - the upright ones with vacuum columns (yeah,
it's trivial ... not!)
 handling "washing-machine" exchangeable disk packs
 ensuring fanfold paper stacks correctly from a fast line-printer
 having the reactions to hit the stop button on that printer when it starts
page-throwing at maximum speed.
 recognising the progress of jobs from the sound of the console loudspeaker

 knowing which boards to tap (and how hard) when doing "preventative
maintenance" listening to that loudspeaker while running the diagnostics
programs (and those programs were probably the very first things to get
thrown out when the computer was replaced)
 switching things on (and off) in the correct order (and how to start the MG
set)
 even the bootstrap sequence wasn't as simple as on a PDP-11


> I would claim that anybody who _truely_ understood a modern
> machine would have no problems on an older one. The fact that very few
> people understand modern computers is the problem, not that the older
> machines are so different.

I would put this the other way round - people who had a good understanding
of the old machines have some chance of getting a deep understanding of
modern ones. In terms of the Instruction Set Architecture and programming
there are few difficulties in understanding one given the other (but for
'minor' things like self-modifying code and the concept of overlays). On the
other hand, the lower level descriptions of the processor logic typically
use terminology that is totally foreign to the modern logic designer - not
to mention the implicit "wired-or" that is frequently used and not
explicitly mentioned in the documentation or that with only a small number
of logic gates per card techniques were used to minimise the number of gates
that would never be seen on modern synchronous logic.

Andy
Received on Sun May 25 2003 - 04:41:00 BST