Drum vs. Core
andyh at andyh-rayleigh.freeserve.co.uk
Mon Jul 2 15:43:49 CDT 2007
Initially most were printing terminals with
lights inside, not Teletypes, can't remember the maker's name.
There was also just two CRT terminals, on which you typed a load of lines
and told the computer to read it.
Could well have been "genuine" ICL block-mode terminals
Do you think the drum got kicked out when we went over to the 4S?
Probably when they went to a dual '4S configuration -
they really tried to have a resilient system - each 4S had its own
motor-generator set and _all_ the peripherals were "Y"-switched.
The flaw in the configuration only appeared when the power-supply
to the Y switches failed :-(
[actually, they could have kept running even then, but the Engineers
naturally refused to work on that without turning the power off]
Was it really that slow! We really put up with a lot back then.
I've still got the timings from the acceptance benchmarks and
have run the same benchmarks on many machines since.
** the most important of these benchmarks was the original "Whetstone"
benchmark - Fortran carefully crafted to not be optimisable*1 - in fact
in ran slower on the optimising compiler than on the standard one.
*1 eventually (20 years later) compiler technology did manage to
optimise away much of the code.
> (I think they were still, however, written in engineers assembler
> which used
> numeric op-codes rather than the mnemonics of PLAN or GIN5).
Interesting. Maybe it was like my school maths teachers who forced us
to use fountain pens instead of ball points because it slowed us down
so we thought more about what we were doing and so made less
No - it was that the engineers _knew_ the ciruit diagram of the processor
and "000 3 100" was more meaningful to them than "LDX 3 base", say.
Very difficult. I had always assumed the executive lived at a fixed
position in memory. Maybe it used relativisers, 1300 style, where
every instruction could specify what block start address should be
added to it, but maybe that would slow down loading the overlays too
The fixed part of Exec loaded at 0 - but the overlays could be on any
64-word boundary.(actually, probably 128 word - but the code would have
on a 54 word boundary)
I wonder if any of the concepts in the 1302 executive got re-
used on 1900.
I don't know, but I doubt it - wasn't the 1300 series a Stevenage design,
while the earliest 1900s came from West Gorton (well, actually the
earliest 1900 was the Canadian FP6000).
Different parts of ICL had very much a "not invented here" attitude and
the previous West Gorton product was Atlas.
Maybe ICL had been bumping up the maintenance charges for old kit
they really did not want to support any more.
That wouldn't have affected us - we had our own engineers and did
our own maintenance. I suspect we were the only none-MOD site
in that position. I wish I had saved more of the engineering documentation -
I probably have enough to make a very close approximation on a FPGA,
but there doesn't seem to be a survivng operators Exec for a 1900,
only George 3 stuff.
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