value of RK05

From: Bill Pechter <pechter_at_pechter.dyndns.org>
Date: Tue May 9 21:09:10 2000

> > >
> > > Err, and just what _production_ PDP11s are pre-11/20??
> > >
> >
> > Gordon Bell had 300 "PDP-11" minicomputers made that were *slightly*
> > different from the PDP-11/20. Most 11/20 boards are rev "A". I will list soo
> > the differences - most had to do with the UNIBUS.. but there was some
> > changes to the datapaths as well.
>
> Ah, so they're not really production machines...
>
> As a user/repairer (as opposed to a collector), my views on prototype
> machines and their value is perhaps a little different to others. There
> are some machines that _only_ existed as prototypes and did things that
> production machines never did (examples would be the PDP11/74, PERQ 2T4,
> etc). Those I find very interesting, and would love to obtain (some
> chance..) But when a prototype went into production with a few changes,
> then I'm not particularly bothered about getting the prototype version --
> most likely I'm going to run into some nasty incompatibility sometime...
>
> -tony
>

The 11/74 was a little more than a prototype since a number of KB11-CM's
were built and implemented internally in DEC. The parts were assigned
real part numbers and were produced in limited quantities.

These 11/74's were pressed into 11/70 service when DEC couldn't meet the
demand for Telco (i.e. AT&T) 11/70's due to the FCC specs in the mid
'80's. They were allowed to sell refurb machines -- so the 11/74's from
internal sites in Massachusetts and New Hampshire were s shipped to the
field to replace Field Service and Software (and in our case the Mid
Atlantic Region Sales) administrive machines in DEC so the 11/70's
running RSTS/E (usually) could be refurbed and shipped to AT&T sites.

They even swapped cusomers for Vax 11/780 systems to get these 11/70's
back from the field.

My biggest fear was backplane failure -- since there were a couple of
11/74 board sets in the country -- but no one knew if there were any
backplanes out there and the 11/70 backplanes got real creaky after 10
years or so of field maintenance.

bill
-- 
bpechter_at_monmouth.com      |     Microsoft: Where do you want to go today?
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Received on Tue May 09 2000 - 21:09:10 BST

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