22 Oct
1999
22 Oct
'99
7:20 a.m.
-----Original Message-----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Friday, October 22, 1999 2:49 PM
Subject: Re: OT: how big would it be?
pcbs at
> I liked Hans's suggestion (which I have now
deleted, alas) of a museum
exhibit
> with three identical computers, but with processor
as single chip, board
of
> gates, and rack of trannies for comparison. It
does provide a service
that you
couldn't
get another way...
... or could you? Didn't PDP8 come in all three versions?
Yes it did, but there were _slight_ differences in the instruction set
IIRC (rather like the differences in the PDP11 instruction set between
similar-ish models).
But having a straight-8, a PDP8/e and a DECmate all running side by side
would be an interesting exhibit. Pity I can't do it...
If we consider calculators for a moment, you can get 2 out of the 3
machines by :
Casio AL1000 (discrete transistor, programmable, not scientific)
Casio AL2000 (ICs, much the same functionality as the AL1000)
???? (All-in-one-chip equivalent)
Or :
HP9100 (discrete transistors, programmable, scientific)
??? (Equivalemt with simple ICs)
HP65 (Almost the same functionality in a handheld)
Only worrying thing would be putting the AL2000 and the HP9100 alongside
each other. They're almost the same size, but the HP uses 'older'
technology and does a lot more...
>
> I've often wondered if you could build a transistorised computer without
> all. You know, trannies on tag board, little
plugs bolted onto the ends
(or on
Of course you could, but why would you want to? What's the problem with
PCBs (or am I going to find out for myself when I get seriously into
making them at home?)
Making PCBs at home is a rediculous waste of time. I have a vacuum lightbox
here as well as a commercial processing system, a silkscreening set up, even
a wave solder machine in my home and nothing compares to what the big guys
can do and charge for the same thing. My last *production* company use to
make its own prototype doublesided PCBs in house and it wasn't worth it. I
have a company I use now that will make me a double sided PCB, GOLD PLATED
contacts, solder mask both sides (pre-drilled of course), and silk screened,
and cut for less than a $1 a board in quantities of 500.
Pre-sensitised boards are useless as they usually come flawed and the
coating thickness is not consitant. The company I use now for PCBs used a
"roll" of sentised film that was "ironed" onto a 3' X 3'
board. Far better
process.
Don't forget a good GERBER and NC drill file is needed and most PCB
manufacturers find little problems with the files that you may not uncover
in
-tony