Bill
... and thereby put the wait light out[1]. Having been brought up with DOS
(the original DOS), and, generally, S/360 Model 30s, I was used to knowing
how busy the machine was by observing the flickering of the wait light.
A few years later, for reasons best kept secret to spare the salesman's
blushes, I was involved in a benchmark of a customer program on a smaller
machine than the one the customer already had. The team was given an
existing assembler program and we were allowed to "tune" it. The
competition - whose active noses had initiated the exercise - had to rewrite
completely in their chosen language: COBOL.
First the I/O buffers were increased and the run time halved. Then I - the
mug - did rewrite the whole program using register arithmetic rather than
the original packed decimal, thereby reducing, say, 15 minutes to 13
minutes. Then I rewrote the whole program yet again reducing the number of
tape passes to 2 from 10. Maybe 15 seconds was now removed from the run
time.
I missed the wait light. The operating system was BPS tape and, in essence,
what BPS does is go into an enabled loop - similar to the BR 15 no doubt. If
one imagines what the wait light would have shown, clearly the original
version of the program hardly affected the wait light's brightness, the I/O
buffers change dimmed it considerably, the arithmetic change almost
extinguished it and the massive logic adjustment to limit the tape passes
extinguished it completely. If I had seen an almost extinguished wait light
after the arithmetic change, it is likely I would have realised there was no
more improvement possible and another major rewrite was pointless.
Chris Mason
[1] Is there still such a light on today's processors and, if not, which
historical S/360+ range removed the indicator?
----- Original Message -----
From: "(IBM Mainframe Discussion List)" <[EMAIL PROTECTED]>
Newsgroups: bit.listserv.ibm-main
To: <[email protected]>
Sent: Friday, June 22, 2007 4:49 PM
Subject: Re: Operating systems are old and busted
In a message dated 6/21/2007 8:14:33 P.M. Central Daylight Time,
[EMAIL PROTECTED] writes:
So the operators used to put DEBE
in and let it crank the meter while they played hearts, but management
was
happy that they used 4-5 hours of machine time. I wouldn't do it and got
called on the carpet for not getting more work done. Ah the good ol days!
I wrote a little program once to do the same thing - i.e., a batch job to
soak up all CPU time. I called it IEFBR15. If you gave it a great big
TIME=
value, it would run for an extra special long time.
Bill Fairchild
Plainfield, IL
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