15 Apr
1998
15 Apr
'98
9:53 a.m.
<"In the PDP-11 family, all operand addressing is accomplished through
<the eight general purpose registers."
<
<If I understand correctly, even things like immediate operands and
<addresses are represented as an addressing mode of a register, namely
<the PC. I think this is quite cool.
Same for stack relative access.
The PDP-11 archetecture was an example of CISC to the max for 16 bit
machines, compared to most micros it has more and richers instruction
set, addressing modes and highlights what can be attained when all
registers are general. Added to a two address structure those registers
and addressing modes make for flexibility and programming power.
...yes a PC relative jump could easily be done with an add r7!
<What do people here on the list think of the flexibility and
<generality of the PDP-11's addressing modes? Is this a well thought
<out architecture in your view? How are the PDP-11's addressing modes
<better or worse than those of other processors, past and present?
Personally I consider it a high point in 16 bit computing and one that
is a standard of comparison. VAX carried this to the 32bit realm. I
know of few 16 bit microprocessors that are as capable as the PDP-11
and as fast (the ti9900 was good but slow, Z8000 was close). The
various chip versions of the PDP-11 (lsi11, T11, F11, J11) have achieved
performace exceeding many of the conteporary microprocessors in code
density and execution speed. The PDP-11 and the C language are an
excellent match, both for addressing modes and effienctcy of compilation.
It is also a good foundation for FORTH.
Terrible cpu, we should junk them all... ;-) ...so I can collect them.
Allison
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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.
(They're also old and will eat you out of house and home with their appetite
for electricity. :)
Has anyone looked at the possibility of retrofitting older pdp11's with modern
switching power supplies to ease the electricity demands...?
(donning asbestos suit in anticipation of cries of "heretic" and
"Frankenstein"...)
Yep, does work. (I had always been promising Steven that I would get
the FP emulator working so I could run it on my FP-less 11/44, but
I got a FP board before I got the emulator going. So you need the FP
board for a 11/44, still!)
Tim.
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Which would be the ones to look out for for practical unix use?
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.
From Milo Velimirovic <milov(a)toes.its.uwlax.edu>
Wed Apr 15 23:17:47 1998
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From: Milo Velimirovic <milov(a)toes.its.uwlax.edu>
Date: Wed, 15 Apr 98 08:17:47 -0500
To: pete(a)dunnington.u-net.com
Subject: Re: PDP-11 Newbie Alert --- (gotta start somewhere)
Cc: pups(a)minnie.cs.adfa.oz.au
Reply-To: milov(a)toes.its.uwlax.edu
References: <199804141844.OAA03748(a)seedlab1.cropsci.ncsu.edu>
<9804150331.ZM9568(a)indy.dunnington.york.ac.uk>
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Hi,
Begin forwarded message:
[snip]
On Apr 14, 14:44, Robert D. Keys wrote:
[snip]
Also, I see pdp-11ish things in surplus around
here quite often.
What would be needed to cobble together a system, for a minimal system 7
sort of box to play with? If there were a list of required boards and
chassis for various levels of system, that might help a newbie get some
sort of machine together.
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.
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.
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.
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 :-)
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
---
Milo Velimirovic <Milo.Velimirovic(a)uwlax.edu>
Unix Computer Network Administrator (608) 785-8030
Information Technology Services -- Network Services
University of Wisconsin - La Crosse
La Crosse, Wisconsin 54601 USA 43 48 05 N 91 14 22 W
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From Tim Shoppa <shoppa(a)alph02.triumf.ca> Thu Apr
16 01:03:00 1998
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From: Tim Shoppa <shoppa(a)alph02.triumf.ca>
Message-Id: <9804151403.AA13468(a)alph02.triumf.ca>
Subject: Re: PDP-11 Newbie Alert --- (gotta start somewhere)
To: pups(a)minnie.cs.adfa.oz.au
Date: Wed, 15 Apr 1998 07:03:00 -0800 (PDT)
In-Reply-To: <9804151317.AA04337(a)toes.its.uwlax.edu> from "Milo
Velimirovic" at Apr 15, 98 08:17:47 am
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Has anyone looked at the possibility of retrofitting
older pdp11's with modern
switching power supplies to ease the electricity demands...?
(donning asbestos suit in anticipation of cries of "heretic" and
"Frankenstein"...)
It's hardly heretical - all Unibus 11's have always had switching
power supplies for the high-current (+5V and - for core machines - +20V)
lines. Depending on the exact model, +15 and/or -15 may have come
from a linear power supply, but these are very low-current lines and
not a major factor in power consumption.
The way to greatly reduce the power consumption of a big Unibus -11
is to go to a more modern CPU and memory in the original backplane.
For an extreme example, a 11/70 with 2 MW of core memory in MJ11 boxes
will draw about 70 Amps at 120 VAC, for over 8kW of power consumption.
But you can replace the 11/70 CPU set with a Quickware replacment
and take the CPU part of power consumption down to 3 or so Amps at
120 VAC, or under 0.4kW.
As to operating
system versions, 2.11BSD needs at least an 11/73 or 83 to run,
How about an 11/44? From Tim Shoppa <shoppa(a)alph02.triumf.ca> Thu Apr
16 01:06:41 1998
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From: Tim Shoppa <shoppa(a)alph02.triumf.ca>
Message-Id: <9804151406.AA09801(a)alph02.triumf.ca>
Subject: Re: PDP-11 Newbie Alert --- (gotta start somewhere)
To: pups(a)minnie.cs.adfa.oz.au
Date: Wed, 15 Apr 1998 07:06:41 -0800 (PDT)
In-Reply-To: <9804150331.ZM9568(a)indy.dunnington.york.ac.uk> from "Pete
Turnbull" at Apr 15, 98 02:31:22 am
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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.
One important point to note is that if you want support for modern MSCP
disk devices, you want to go with 2.11BSD. The most modern disk devices
supported by 7th Edition are the RL02 and the various Massbus disks.
Tim. (shoppa(a)triumf.ca)
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From "Robert D. Keys"
<rdkeys(a)seedlab1.cropsci.ncsu.edu> Thu Apr 16 00:25:26 1998
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From: "Robert D. Keys" <rdkeys(a)seedlab1.cropsci.ncsu.edu>
Message-Id: <199804151425.KAA04925(a)seedlab1.cropsci.ncsu.edu>
Subject: Re: PDP-11 Newbie Alert --- (gotta start somewhere)
In-Reply-To: <9804151317.AA04337(a)toes.its.uwlax.edu> from Milo Velimirovic at
"Apr 15, 98 08:17:47 am"
To: milov(a)toes.its.uwlax.edu
Date: Wed, 15 Apr 1998 10:25:26 -0400 (EDT)
Cc: pete(a)dunnington.u-net.com, pups(a)minnie.cs.adfa.oz.au
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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. (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. >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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From "Steven M. Schultz"
<sms(a)moe.2bsd.com> Thu Apr 16 01:22:57 1998
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To: pups(a)minnie.cs.adfa.oz.au
Subject: Re: PDP-11 Newbie Alert --- (gotta start somewhere)
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Milo -
Hi.
From: Milo Velimirovic
<milov(a)toes.its.uwlax.edu>
How about an 11/44?
Indeed the 11/44 will work and very well with 2.11BSD. Before the
one at work got shutdown (RA81 failure and the support department here
doesn't like PDP-11s and refuses to help fix it) the care and feeding
of 2.11 was shared between a 11/44 (for UNIBUS related stuff) and a
11/73 (for QBUS).
The 11/84 and 94 will also work very well. Qbus models from the 11/53
on up will also work (the 53 hasn't actually been 'tested' but
"should"
work, the 73, 83, 93 are all known to work).
While the 11/45 has the MMU aspects required (split I/D and supervisor
mode) it doesn't support enough memory. The 11/45 can only have 248kb
of memory and a full 2.11 kernel+networking+diskcache+datastructures
setup weighs in at almost 400kb
Steven
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