PDP-11 Newbie Alert --- (gotta start somewhere)

[Robert D. Keys]

> >There are so many permutations, it's hard to make a list.  There are two
> >general classes of PDP-11, QBus and Unibus.  Most even-numbered models are
> >Unibus, most odd-numbered models are QBus (but not all).  QBus machines tend
> >to be smaller.
> 
> QBUS 11/2 11/03 11/23 11/53 11/73 11/83
> Unibus 11/05 11/10 11/15 11/20 11/24 11/3411/35 11/40 11/44 11/45 11/55
>        11/60 11/70 11/84...
> 
> Odd numbered machines where the odd digit is a 5 are usually a Unibus machine.

Which would be the ones to look out for for practical unix use?

> (They're also old and will eat you out of house and home with their appetite
> for electricity. :) 

I have heard that from the computer students around here who chuckle at
the thought that I would attempt to run such a beastie.  They are chasing
Alphas and Pentiums, whilst I am chasing pdp11s?  Interesting directions.

For the sake of discussion, what sorts of power requirements would be
required for a lowend version 7 or 2.11 BSD box?  Say that I wanted
a machine that would allow me to troff/Tex a little, and do some
minor C compiling, associated with that.

> Has anyone looked at the possibility of retrofitting older pdp11's with modern
> switching power supplies to ease the electricity demands...?  

I often use old DEC linear power supplies to run some of my antique radio
equipment.  The power supplies themselves are not that much of an efficiency
thing, but the loads probably are.  Minimizing unneeded loads on a home
system would be of merit.  That is why I was wondering what sort of mininmal
box would do for home use, and still give some kind of reasonable service.
The electicity mongers need to be fed, but I don't need to treat them
to a full 7 course meal every day.

Are there special electrical requirements?  I can always find a separate
20 or 30 amp 115 volt circuit, but the 220 lines are tied up in my
antique radio transmitters.  Just how hungry are these pdp11s?

> (donning asbestos suit in anticipation of cries of "heretic" and
> "Frankenstein"...)

Don't worry, I still keep my ol' net asbestos flak suit hanging up in the
corner, for occasional donning.....(:+}}....  It is a little dusty.
It be faire windes and following seas about the net mostly, these days.
I consider it great fun to resurrect the old dinosaurs.  I still keep
a few 8 inch CP/M S-100 boxes running, for fun.  Alas, finding parts is
always a problem, anymore, especially in the deep south where silicon
valley ain't.  You have to make do with what you can cobble together.
I find that I mix and mash parts from old surplus radio equipment, 
computers, or whatever until I can make the thing work.  That is as
much the fun of it as actually watching the platters whirr and spin.

> >As to operating system versions, 2.11BSD needs at least an 11/73 or 83
> >to run,
> 
> How about an 11/44? 
> 
> >as it needs memory management with separate address spaces for instructions
> >and data.  7th Edition will also run on those machines, and if the kernel is
> >suitably compiled, will also run on smaller machines such as 11/23s, which
> >are quite common.  Early versions will run on a whole range of models.

What exactly were the Heathkit things in relation to the mainstream pdp11s?
There was a unix that was available on the Heathkit boxes, but I never did
get enough money together at the time to get one --- had to settle for that
CP/M thingie, instead.

> >Whatever you get, you'll need a processor (which might be a single card or as
> >many as ten), memory (256K will do fine for 7th Edition, but more is better),
> >at least one serial line unit for a terminal (or PC with terminal emulation
> >software), and a disk controller with a suitable hard disk.  Here again there
> >are lots of possibilities, you want at least 10MB for 7th Edition and a lot
> >more for BSD.

What would BSD be comfy with, with a little space for play.  I remember
the old Xenix boxes that we had (RS 16B things) ran a sort of v7 in about
15 megs HD.  The FreeBSD things require 100 or so megs to come up.
What sizes of HD would one be looking out for, in the surplus piles?

> >Others may wish to expand on what I've written.  Personally, I'd go see what
> >you can find, describe it to the list, and wait for the 101 pieces of advice
> >you'll get from all of us about its suitability/desirability :-)

I enjoy all the advice and comments.

Thanks to all for them.

Bob Keys


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