17 Jan
2017
17 Jan
'17
1:10 a.m.
I was well aware of the comment in V6, but had no idea what it
referred to. When Dennis and I were porting what became V7 to the
Interdata 8/32, we spent about 10 frustrating days dealing with savu
and retu. Dennis did his most productive work between 10pm and 4am,
while I kept more normal hours. We would pore over the crash dumps
(in hex, then a new thing for us--PDP-ll was all octal, all the
time). I'd tinker with the compiler, he'd tinker with the code and
we would get it to limp, flap its wings, and then crash. The problem
was that the Interdata had many more registers than the PDP-11, so the
compiler only saved the register variables across a call, where the
PDP-11 saved all the registers. This was just fine inside a process,
but between processes it was deadly. After we had tried everything
we could think of, Dennis concluded that the fundamental architecture
was broken. In a couple of days, he came up with the scheme that
ended up in V7.
It was only several years later when I saw a T-shirt with savu and
retu on it along with the famous comment that I realized what it had
referred to, and enjoyed the irony that we hadn't understood it
either...
Steve
----- Original Message -----
From: "Brantley Coile" <brantleycoile(a)me.com>
To:"Larry McVoy" <lm(a)mcvoy.com>
Cc:<tuhs@tuhs.org>
Sent:Mon, 16 Jan 2017 05:11:02 -0500
Subject:Re: [TUHS] Article on 'not meant to understand this'
17 Jan
17 Jan
2:15 a.m.
New subject: PDP-11, Unix, octal?
On Mon, Jan 16, 2017 at 11:10:37AM -0800, Steve Johnson wrote:
We would pore over the crash dumps (in hex, then a
new thing for us -- PDP-11 was all octal, all the time).
Something I've been meaning to ask for a while: why Unix and octal on the
PDP-11? Because of the DEC documentation?
I understand why other DEC architectures (e.g. PDP-7) were octal: 18b is
a multiple of 3. But PDP-11 is 16b, multiple of 4.
After all, Unix had its own assembler, so was there a need/reason to
use octal?
Cheers, Warren
2:25 a.m.
New subject: PDP-11, Unix, octal?
Warren Toomey wrote:
I understand why other DEC architectures (e.g. PDP-7)
were octal: 18b
is a multiple of 3. But PDP-11 is 16b, multiple of 4. After all, Unix
had its own assembler, so was there a need/reason to use octal?
Octal is a natural fit for the instruction set encoding.
4:31 a.m.
New subject: PDP-11, Unix, octal?
octal was also a good fit for a lot of the other dec systems of the time,
notably the 8 and the 10. I actually found octal to be a pain in the neck
on the -11: values and addresses were 377, or 177777 and 377777 and ...
bleah. I was glad when hex came along.
On Mon, Jan 16, 2017 at 1:04 PM Lars Brinkhoff <lars(a)nocrew.org> wrote:
Warren Toomey wrote:
I understand why other DEC architectures (e.g.
PDP-7) were octal: 18b
is a multiple of 3. But PDP-11 is 16b, multiple of 4. After all, Unix
had its own assembler, so was there a need/reason to use octal?
Octal is a natural fit for the instruction set encoding.
2:31 a.m.
New subject: PDP-11, Unix, octal?
When I learned DG NOVA assembler in the mid-1970s, octal was it - it was everywhere. I
didn't see hexadecimal notation until 8-bit microcomputers started using it in the
late 1970s and early 1980s.
Just a change in culture, I'd suppose. Hex fits neatly into a byte, and we don't
seem to see computers with word sizes that aren't a multiple of 8 any more.
Erik <fair(a)netbsd.org>
7:09 a.m.
New subject: PDP-11, Unix, octal?
The mainframes of the 60's and 70's all used 6-bit characters (and
often different encodings for the non alphanumeric characters). So
the Unix folks, including me, had experience with octal long before
Dec.
Steve
----- Original Message -----
From: "Warren Toomey" <wkt(a)tuhs.org>
Something I've been meaning to ask for a while: why Unix and octal on
the
PDP-11? Because of the DEC documentation?
7:33 a.m.
New subject: PDP-11, Unix, octal?
And DEC used octal from the 1959 PDP1 through the VAX which was
announced on October 1977.
The PDP11 register front panel was painted to make front panel octal
programming easier - breaking out the three bit patterns.
Octal was deep in the DEC history and front panel flipping fingers.
I'll never forget 014747 (single instruction memory decrement test (move
the pc to address pc - 2...
Bill
Steve Johnson wrote:
The mainframes of the 60's and 70's all used
6-bit characters (and
often different encodings for the non alphanumeric characters). So the
Unix folks, including me, had experience with octal long before Dec.
Steve
----- Original Message -----
From:
"Warren Toomey" <wkt(a)tuhs.org>
Something I've been meaning to ask for a while: why Unix and octal
on the
PDP-11? Because of the DEC documentation?
--
Digital had it then. Don't you wish you could buy it now!
pechter-at-gmail.com http://xkcd.com/705/
8:28 p.m.
New subject: PDP-11, Unix, octal?
"Steve Johnson" <scj(a)yaccman.com> wrote:
The mainframes of the 60's and 70's all used
6-bit characters (and
often different encodings for the non alphanumeric characters). So
the Unix folks, including me, had experience with octal long before
Dec.
Bit IIRC, this has been done with 10 6 bit chars in a 60 bit word.
Did people use octal in this area?
Jörg
--
EMail:joerg@schily.net (home) Jörg Schilling D-13353 Berlin
joerg.schilling(a)fokus.fraunhofer.de (work) Blog: http://schily.blogspot.com/
URL: http://cdrecord.org/private/ http://sourceforge.net/projects/schilytools/files/
9:14 p.m.
New subject: PDP-11, Unix, octal?
Joerg Schilling asks today:
> this has been done with 10 6 bit chars in a 60 bit
word.
> Did people use octal in this area?
I worked on a CDC 6400 with both NOS and KRONOS operating systems in
the 1970s. The 6400/6600/7600 family were definitely in the octal
world. Initially, the character set was 6-bit, with one character
reserved as an escape to mean that the next 6-bit chunk was to be
included, giving a 12-bit representation that added support for
lowercase letters (a feature that we could only get on our IBM 360 and
Amdahl 470 mainframes with a once-a-night change of the line printer
glyph chain).
Here is a quote by the lead architect, James E. Thornton, who wrote
the 1970 book, ``Design of a Computer: the Control Data 6600'', and
the 1980 history paper ``The CDC 6600 Project''
(http://dx.doi.org/10.1109/MAHC.1980.10044)
> The selection of 60-bit word length came after a
lengthy
> investigation into the possibility of 64 bits. Without going
> into it in depth, our octal background got the upper hand.
That comes from page 347 of the paper.
-------------------------------------------------------------------------------
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- University of Utah FAX: +1 801 581 4148 -
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-------------------------------------------------------------------------------
10:53 p.m.
New subject: PDP-11, Unix, octal?
On 17Jan 2017, at 10:14 AM, Nelson H. F. Beebe
<beebe(a)math.utah.edu> wrote:
the 1970s. The 6400/6600/7600 family were definitely in the octal
world. Initially, the character set was 6-bit, with one character
reserved as an escape to mean that the next 6-bit chunk was to be
included, giving a 12-bit representation that added support for
lowercase letters
We called it “half-ASCII”, escaping with codes 74B and 76B. As far as I recall, it only
worked
on some versions of some of the timesharing systems in some modes. We never had a lower
case print chain at Lehigh, SO ALL OUR OUTPUT WAS IN UPPER CASE.
And don’t get me started on 63- vs 64- character set.
The availability of ASCII on other operating systems was a great improvement in my life.
And certain neurons still remember crap like 22B is R in display code.
ches
8:12 p.m.
New subject: PDP-11, Unix, octal?
Warren Toomey <wkt(a)tuhs.org> wrote:
On Mon, Jan 16, 2017 at 11:10:37AM -0800, Steve
Johnson wrote:
Note that the people wo did this, used the 18 bit machines before.
Jörg
--
EMail:joerg@schily.net (home) Jörg Schilling D-13353 Berlin
joerg.schilling(a)fokus.fraunhofer.de (work) Blog: http://schily.blogspot.com/
URL: http://cdrecord.org/private/ http://sourceforge.net/projects/schilytools/files/
We would pore over the crash dumps (in hex,
then a
new thing for us -- PDP-11 was all octal, all the time).
Something I've been meaning to ask for a while: why Unix and octal on the
PDP-11? Because of the DEC documentation?
I understand why other DEC architectures (e.g. PDP-7) were octal: 18b is
a multiple of 3. But PDP-11 is 16b, multiple of 4.
After all, Unix had its own assembler, so was there a need/reason to
use octal?
9:28 p.m.
New subject: PDP-11, Unix, octal?
On Tue, Jan 17, 2017 at 6:12 AM Joerg Schilling <schily(a)schily.net> wrote:
Note that the people wo did this, used the 18 bit machines before.
As steve johnson pointed out, just about everything around then was octal.
I think IBM brought widespread use of hex with the 360 ca. 1964, but to
most other vendors octal was a way of thinking as your interesting quote
points out.
As for character formats, on e.g. the pdp-10 you had lots of choice,
including 6 6-bit chars or 7 5-bit chars with one bit left over as common
... I also recall people used to complain about the inefficiencies inherent
in 8-bit character formats ...
I for one was still pretty glad to see octal mostly go away.
ron
2895
days inactive
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11 comments
9 participants
participants (9)
-
Erik E. Fair -
Lars Brinkhoff -
Nelson H. F. Beebe -
ron minnich -
schily＠schily.net -
Steve Johnson -
Warren Toomey -
William Cheswick -
William Pechter