Getting out of the hobby

[jim stephens]

On 10/13/2016 9:39 PM, tony duell wrote:
> Actually, it wasn't. I have been a member almost from day 1, and my first
> question to the list founder (I think it was Selam) was 'Are minicomputers
> welcome on the list, or is it micros only?'
Earliest I could find (I think)

 From ard12 at eng.cam.ac.uk *Wed Apr  2 20:42:09 1997*
From: ard12 at eng.cam.ac.uk (*A.R. Duell)*
Date: Wed, 02 Apr 1997 20:42:09 BST
Subject: How long will they last?
In-Reply-To: 
<Pine.ULT.3.91a.970331175254.2754A-100000 at booster.bothell.washington.edu>; 
from "Bill Whitson" at Mar 31, 97 6:01 pm
Message-ID: <199704021942.12089 at club.eng.cam.ac.uk>

 >
 >
 > I was talking to a friend this weekend who brought
 > up this idea that before long EPROMs in our old
 > computers are going to start to go bad.  This is
 > something I've heard before but, to be honest, I
 > don't know enough to make a judgement on it.  If
 > this is the case, I suppose I should be burning
 > backups.

Don't bother with burning backups (after all, the backup will only last
another 10 years), but dump the data (as a plain binary file) to a
suitable archival storage medium.

What I recomend is _before_ even powering up a machine is to dump all the
ROMs, the PALs (an amazing number of classic computers have
non-copy-protected PALS), etc to a PC-format disk. Then punch any really
rare stuff onto paper tape (You may laugh, but I've _never_ found a paper
tape that I can't read, and EPROM files are not that big in general). If
the chips ever fail in the future, then It's easy to burn a new EPROM
then.

 >
 > While I'm at it... What are some other concerns
 > along these lines.  What should we be planning
 > for as these machines grow 5, 10, 15 years  older?

Well, there's no problem with standard electronic parts (resistors,
capacitors, TTL chips, etc). I don't think you'll have any problems
finding those in 15 years time.

Other chips are more of a problem. AMD2900 bit-slice chips are getting
hard to find, and a lot of minicomputers and their peripherals depend on
them. But I'm not sure that if I buy any now they'll still be good in 10
years time.

ASICs are a big problem. Basically, there's no hope if they fail. You
can't copy them at home. The best thing to do is to figure out _exactly_
how they work, the timing of all the signals, etc, and to record that. If
the chip fails, and you can't get one, then at least you can make a clone
out of TTL or something like a Xilinx FPGA.

I'd also recomend recording any information now that would be of use if
the machine failed. If you know what you are doing, note down the voltages
on the CRT electrodes in a monitor. The waveforms in the PLL of a disk
controller, that sort of thing. Basically, annotate the service manual
with details of _your_ machine.

 >
 > Bill Whitson
 > ClassicCmp "owner"
 > bcw at u.washington.edu   bill at booster.u.washington.edu
 >


--
-tony
ard12 at eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill