-----Original Message-----
From: Tony Duell <ard_at_p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Friday, October 22, 1999 2:49 PM
Subject: Re: OT: how big would it be?
>> 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
pcbs at
>> 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
>
Received on Fri Oct 22 1999 - 14:20:24 BST