[...]
>And there are some minis in there amongst the micros:
>
>An HP 2100A CPU. Unfortunately it is the CPU only. No I/O, no
>memory, no peripherals to speak of. Did get the CPU manuals with it,
>though, and they have made interesting reading and probably will one
>day again. I am not actively seeking the other bits right at the
>moment but am keeping my eyes open.
I found one of those in a skip (literally!) a few years back, and was allowed
to rescue it. Mine came as the CPU box with 32K (I think) core, a lot of I/O
cards (or at least I assume that's what they are), a paper tape reader and a
somewhat mangled cartridge disk drive (1 fixed platter, one RK05-like
cartridge). Alas no manuals.
It looks like it could be got to run again, but as I know nothing about it,
I've not put any time in on it yet....
>
>Now *that* is sad: I am ignoring good stuff that I could probably
>learn something about, maybe even learn something useful from. But I
>am already having to come to terms with the fact that there is a lot
>of stuff to learn, probably more than I can fit into one lifetime. Or
>maybe I've just got a bad case of hardening of the brain? I don't
>know.
>
>But I wonder how many other folks out there think to collect things
>that they know stuff about, as opposed to stuff they don't know
>anything about? I have to admit, the former makes a narrower
>selection filter and the latter has gotten me into, um, unexpected
>learning experiences (yeah, that's it) more often than not. And
>for most people the "things they know stuff about" is more likely to be
>micros than minis.
I swap between the 2 'modes'. Sometimes I'll get a machine because I know what
it is, and because I remember it. The Tandy M4 I bought a couple of weeks ago
fits in here - I grew up on a Tandy Model 1, and remember the M4 coming out. I
wanted one then, but could never afford it. Now I can, and can run those
programs from 80-micro....
But more often I get a machine because I have no idea what it is, but it looks
interesting. The P850 (the machine that seriously started me collecting) fits
in here. As do the PERQs - I thought it was a 68000 box when I got the first
one, and was amazed to see a soft-microcoded CPU. Learning from such a machine
is great fun...
[...]
>(Yes, I am apt to collect this sort of documentation in the absence of
>hardware too -- I am more a programmer than a hardware guy and I
I certainly grab schematics and printsets without the hardware that goes with
them - you never know what will turn up later....
>mostly understand computers in terms of how to wrangle code for them.
>And I really stand in awe of folks like you who can understand them in
>terms of hardware too -- another thing that is on my to-learn list.)
It's not that hard. What started me off was getting a relatively simple
minicomputer - I'd recomend either the PDP8/e or the PDP11/05 as a starter, and
sitting down with the machine, the technical manual, and the printsets. I
single-stepped the machine, and watched how it executed an instruction with a
logic probe. I where the microcode went, what gates were enabled, etc, and
related it to the diagrams in the manual. After a couple of days I could
understand most of the instructions....
>Got any pointers to where we could learn more?
Yep...
CPU Technical manuals from the late 1960's - early 1970's. Most of those
include a gate-level description of the CPU operation. It helps a lot to have
the machine in front of you, though.
>
>-Frank McConnell
-tony
Received on Wed Jul 23 1997 - 08:48:32 BST
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