[TUHS] PDP-11 questions

[TUHS] PDP-11 questions

[Noel Chiappa]

    > The later M9301 (see disassembly of the contents here:
    >   http://ana-3.lcs.mit.edu/~jnc/tech/pdp11/M9301-YA.mac
    > of one variant) didn't clear memory either

OK, so _my_ memory is failing! That code does in fact test the memory.

(Although, looking at it, I can't understand how it works; after writing the
contents of R3 into the memory section it it asked to test, it complements the
test value in R3, before comparing it with the memory it just wrote with R3,
to make sure they are the same. Maybe there's an error in the dis-assembly?)

Anyway, it should have left the memory mostly containing all 0's.

	Noel

[TUHS] PDP-11 questions

[Clem Cole]

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On Tue, Jan 26, 2016 at 3:07 PM, Doug McIlroy <doug at cs.dartmouth.edu> wrote:

> > Dr. Wang invented the core memory at IBM BTW
>
> Wang did make a magnetic-core storage device (a 2-core-per-bit
> shift register) but Jay Forrester's core memory, first installed
> on MIT's Whirlwind computer in 1953, is the one that actually
> saw use and very quickly dominated the market.
>
​Excellent. Nice to know.     Thank you,
Clem​
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[TUHS] PDP-11 questions

[Clem Cole]

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On Tue, Jan 26, 2016 at 2:52 PM, Dave Horsfall <dave at horsfall.org> wrote:

>
> Sorry; I wasn't accusing you.
>

​no issues.

​

> But yeah, had I known of prior work then I certainly would have used it
> (with all due credit) instead of re-inventing that particular wheel.

​same here.  The UNIX community has always tended to do what they had to do
and shared as they could and when they knew about it.
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[TUHS] PDP-11 questions

[Doug McIlroy]

> Dr. Wang invented the core memory at IBM BTW

Wang did make a magnetic-core storage device (a 2-core-per-bit
shift register) but Jay Forrester's core memory, first installed
on MIT's Whirlwind computer in 1953, is the one that actually
saw use and very quickly dominated the market.

Doug

[TUHS] PDP-11 questions

[Warren Toomey]

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On Tue, Jan 26, 2016 at 02:36:28PM -0500, Doug McIlroy wrote:
> That is exactly right. Unix was up and running as a time-sharing
> system with remote access before a primitive DOS emerged from DEC.
> The chess problem was enumeration of closed knight tours.

"The processor arrived at the end of the summer [1970], but the PDP-11
was so new a product that no disk was available until December. In the
meantime, a rudimentary, core-only version of Unix was written using
a cross-assembler on the PDP-7. Most of the time, the machine sat in
a corner, enumerating all the closed Knight's tours on a 6×8 chess
board—a three-month job."
	-- https://www.bell-labs.com/usr/dmr/www/hist.html

Cheers, Warren

[TUHS] PDP-11 questions

[Dave Horsfall]

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On Mon, 25 Jan 2016, Clem cole wrote:

> Dave not doubt. Sorry. I didn't  publish.

Sorry; I wasn't accusing you.  It was a couple of bods at UNSW (if they're 
on this list then they know who they are).

But yeah, had I known of prior work then I certainly would have used it 
(with all due credit) instead of re-inventing that particular wheel.

-- 
Dave Horsfall DTM (VK2KFU)  "Those who don't understand security will suffer."

[TUHS] PDP-11 questions

[Doug McIlroy]

> First, I was wondering when Bell Labs got that first PDP-11/20 what
software (if any) came with it? 

> I have this bit set that they didn't get anything, they wrote a
cross-assembler on another machine. I know that when it came, it didn't have a
disk (wasn't ready yet), so it ran a chess problem (memory only) for quite a
while until the disk came.

That is exactly right. Unix was up and running as a time-sharing
system with remote access before a primitive DOS emerged from DEC.
The chess problem was enumeration of closed knight tours.

Doug

[TUHS] PDP-11 questions

[Clem Cole]

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On Mon, Jan 25, 2016 at 11:18 AM, Pete Turnbull <pete at dunnington.plus.com>
wrote:

> The University of Leeds did something similar - an 11/34 with a lot of
> Emulex serial lines and an RX02 to boot from, was connected to their
> Amdahl. I


​Indeed back in the day that was a very popular PDP-11 configuration at a
lot of places (except UCB who had a giant patch board in each building).
Noel, didn't MIT have something running SupDup?

CMU called this configuration the "terminal front end" or just "Front End"
(FE).  I know commercially the Timeshare guys did this with their PDP-10s -
they called them "terminal switches"  but started with CMU EE/CS version.
 I also remember walking into a computer room in one of the big banks in
NYC and the only DEC equipment was PDP-11 running the terminals -
everything else in the room was big blue.

One of my CMU classmates that went to IBM friends told me that the way the
Series-1 finally got funded at IBM was to try to sell against DEC in just
that market.  He said that it was why the S1 was IBMs first pure ASCII
machine and had RS232C ports (when it first came out IBM did not even
make/sell an terminals that talked to it - most customers were buying
VT-100 or clones).

Also, the CMU Front End was originally two system depending if you were
talking to the University's main Computer Center or to the CS/EE Dept
systems.  Both FE's  were 11/20s originally, then later 40e's but not
connected to each other.  CMU had also designed it's own serial port for
them which we called an ASLI or Asynchronous Line Interface because DH-11
and DL11 ports were too expensive at the time.     As more and more "large
systems" systems (read UNIX based 11's and Vaxen) showed up on campus
(around the time as I was leaving) the "Distributed FE" was being developed
in EE, originally using LSI11s and 3Mb Xerox ethernet.  It was then further
cost reduced to 8085s on multibus boards by Andy Bechtolsheim (which he
later redesigned to use a 68k at Stanford - ie. the Sun board traces it
roots to the PDP-11 being used an embed terminal front-end :-)

Anyway - the key point being made is that the DEC sold a large number of
embedded PDP-11 as a popular way to driving terminals and modem pools into
larger systems.  No DEC SW ran on them -- they were "purpose built."  DEC
pretty much owned that business until finally cheap microprocessors and
cheap ethernet connections displaced them for the tasks.   But in truth,
that really was limited because by the the personally computer and
workstations had begun to replace the "glass TTY."

Clem

​
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[TUHS] PDP-11 questions

[John Cowan]

Johnny Billquist scripsit:

> >That's what I remember.  My first PDP-8 was running EDU30 on top of
> >OS/8.
> 
> Glad we got that sorted. Sorry for the confusion.

Now that I think about it, I think the command to start the EDUsystem
was .R EDU300 rather than .R EDU30, but I don't know why.  The documentation
all said EDUsystem 30.

-- 
John Cowan          http://www.ccil.org/~cowan        cowan at ccil.org
Original line from The Warrior's Apprentice by Lois McMaster Bujold:
"Only on Barrayar would pulling a loaded needler start a stampede toward one."
English-to-Russian-to-English mangling thereof: "Only on Barrayar you risk to
lose support instead of finding it when you threat with the charged weapon."

[TUHS] PDP-11 questions

[Pete Turnbull]

On 25/01/2016 11:29, Tony Finch wrote:
> Norman Wilson <norman at oclsc.org> wrote:
>>
>> It worked both ways, of course.  I too suspect that a
>> majority (though I'm not so sure about `vast') of PDP-11s
>> never ran UNIX.
>
> A random vaguely off-topic example: in Cambridge a PDP-11 was used as a
> terminal multiplexor for the IBM mainframe.

The University of Leeds did something similar - an 11/34 with a lot of 
Emulex serial lines and an RX02 to boot from, was connected to their 
Amdahl. I remember the RX02 particularly because when we decommissioned 
it and took out the floppies, both had completely transparent rings on 
or near track zero, so it obviously had been left running and not 
rebooted in quite some time.  In the same machine room there were two 
third-party cabinets with KDJ11A CPUs, more serial lines and IBM channel 
interfaces. They also had at least one DX11.

The University of Edinburgh used several small PDP-11/23s in BA11-N 
boxes as terminal/network concentrators for EMAS. I can't remember how 
they worked but I remember they had one sync serial interface and a 
bunch of DLV11-Js.

-- 
Pete

[TUHS] PDP-11 questions

[Johnny Billquist]

On 2016-01-25 17:00, John Cowan wrote:
> Johnny Billquist scripsit:
>
>> the desktop models are called MS800A, MS800B, MS880A and MS880B.
>
> Good to know.

I should try and locate whatever document I have that says DECstation as 
well. Fun, if nothing else.

>> Reading through it, it's very clear that this is not OS/8, or any
>> derivative of it.
>
> You're right.  What it did share, however, was the OS/8 file system,
> except that the date epoch was 1972 instead of 1970.  I don't know if
> COS survived long enough to use extended dates.

Sortof. The File system in COS is weird. It do have an sortof OS/8 
compatible file system for the system area, with the different date 
base. But it's not clear if OS/8 would actually be able to read it, as 
the layout of the whole disk is different. COS divide the disk into 
segments, and allocates a bunch of those for the system area, and then 
use the other segments to implement data files.

COS also shares the format of .SV files with OS/8. But I doubt any OS/8 
binary would run under COS. (Well, maybe something that did not use any 
device drivers or USR.)

>> the transfer program
>> available to transfer files to/from OS/8.
>
> That didn't actually transfer files, which wasn't necessary; IIRC,
> it converted between the COS-310 format for text files (about which
> I know nothing) and the OS/8 format (three 8-bit bytes in two 12-bit words,
> packed with the first two bytes in the low order bits of the words,
> and the third byte split between the four high order bits).

Not entirely. Like I said above, COS has a weird layout of mass storage, 
where you have logical files, which are just numbered. And that is how 
most of the mass storage is used. And those files can also be converted, 
and the transfer program deals with that. In addition, I am not sure 
that OS/8 would be able to figure out any COS disk, since I'm not so 
sure the actual location of the directory files and the data is the same 
between them. So even though the directory format itself is the same, 
that is not necessarily enough to be able to exchange disks.

But yes, in addition, text is also encoded in a different way in COS 
text files.

>> The EDUsystems were in fact having numbers
>> like 10, 20, 25, 30, 40 and 50. No 310 or anything close...
>
> That's what I remember.  My first PDP-8 was running EDU30 on top of
> OS/8.

Glad we got that sorted. Sorry for the confusion.

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

[TUHS] PDP-11 questions

[John Cowan]

Johnny Billquist scripsit:

> the desktop models are called MS800A, MS800B, MS880A and MS880B. 

Good to know.

> Reading through it, it's very clear that this is not OS/8, or any
> derivative of it. 

You're right.  What it did share, however, was the OS/8 file system,
except that the date epoch was 1972 instead of 1970.  I don't know if
COS survived long enough to use extended dates.

> the transfer program
> available to transfer files to/from OS/8.

That didn't actually transfer files, which wasn't necessary; IIRC,
it converted between the COS-310 format for text files (about which
I know nothing) and the OS/8 format (three 8-bit bytes in two 12-bit words,
packed with the first two bytes in the low order bits of the words,
and the third byte split between the four high order bits).

> The EDUsystems were in fact having numbers
> like 10, 20, 25, 30, 40 and 50. No 310 or anything close...

That's what I remember.  My first PDP-8 was running EDU30 on top of
OS/8.

> But EDUsystems do not really predate the 8/A. They carried on in the
> PDP-11 systems as well, beyond the 8/A era.

Sure.  What I mean is that the EDUsystems began before the 8/A, not that
they ended before it.

-- 
John Cowan          http://www.ccil.org/~cowan        cowan at ccil.org
Why are well-meaning Westerners so concerned that the opening of a
Colonel Sanders in Beijing means the end of Chinese culture? [...]
We have had Chinese restaurants in America for over a century,
and it hasn't made us Chinese.  On the contrary, we obliged the Chinese
to invent chop suey.            --Marshall Sahlins

[TUHS] PDP-11 questions

[Clem Cole]

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On Mon, Jan 25, 2016 at 8:38 AM, Lawrence Stewart <stewart at serissa.com>
wrote:

> We had one at the Stanford Information Systems Lab sometime in 78 or 79,
> running (I think) V7, and we certainly didn’t do the port ourselves!  We
> did put it on the Arpanet though, as SU-ISL.  This
> was a pretty weird hookup.  The NCP ran on a front-end LSI-11 (or was it
> an 11/23?) and there was
> a Very Distant Host interface home-built by Ron Crane that ran over a
> copper pair to the IMP at the medical school.  I did the driver work to
> connect the 11/34 to the smaller 11 running the NCP.
>

​If it was 78, it was probably v6+ of some sorts running Chesson's Arpanet
NCP from Illinois.​  UNIX/TS (aka V6+++ / pre V7) sorts of oozes out via
the Bell Labs' OYOC like Ted in '78 - that's what we ran at CMU since Ted
brought it with him. Its a heavily hacked V6 kernel and many of what would
become the v7 utilities including the a new compiler and the standard I/O
library.   Same was true of PWB 1.0 - which was based on most of the code.
   Dennis would not formally get V7 (which had an updated kernel) released
until mid '79 (FWIW: The date on a number of the files in the V7
distribution tapes in Warren's archives show Aug 1, '79 - which sounds
about right for when Dennis got it out).
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[TUHS] PDP-11 questions

[Johnny Billquist]

On 2016-01-25 13:54, John Cowan wrote:
> Johnny Billquist scripsit:
>
>> The 310 was not called a Professional, though. It was the EDUsystem
>> if I remember right.
>
> I never heard of an EDUsystem built into a desk; they all predated
> the 8/A.  This was running COS-310, an offshoot of OS/8.
> See Doug Jones's PDP-8 FAQ.

Felt a little bored, so I started digging around some.

In the PDP-8/A mincomputer handbook 
(http://bitsavers.trailing-edge.com/pdf/dec/pdp8/handbooks/MinicomputerHandbook_1976.pdf), 
the desktop models are called MS800A, MS800B, MS880A and MS880B. But I 
know there is some manual that calls them DECsystem as well, but that 
might not be any document that has been scanned. I have paper copies of 
a lot of stuff somewhere in my cellar.

The COS-300/310 system reference manual is on Bitsavers 
(http://bitsavers.trailing-edge.com/pdf/dec/pdp8/cos-300/DEC-08-OCOSA-F_D_COS_300_310_System_Reference_Manual_Jul75.pdf). 
Reading through it, it's very clear that this is not OS/8, or any 
derivative of it. Check the file system details for example, the file 
name syntax (device is added after the filename, with a comma 
separator), various CUSPS like PIP, or the transfer program available to 
transfer files to/from OS/8.

I tried searching around more on COS-310, but only came up with other 
peoples memories (https://en.wikipedia.org/wiki/Talk%3ADIBOL), but which 
also suggested that COS-310 came with the 8/e and later 8/a, including 
in a desktop config.

As for the EDUsystem thing, that must have been my brain. I can't find 
any connections. The EDUsystems were in fact having numbers like 10, 20, 
25, 30, 40 and 50. No 310 or anything close...
But EDUsystems do not really predate the 8/A. They carried on in the 
PDP-11 systems as well, beyond the 8/A era.

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

[TUHS] PDP-11 questions

[Lawrence Stewart]

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Regarding the 11/34.

We had one at the Stanford Information Systems Lab sometime in 78 or 79, running (I think) V7, and we certainly didn’t do the port ourselves!  We did put it on the Arpanet though, as SU-ISL.  This
was a pretty weird hookup.  The NCP ran on a front-end LSI-11 (or was it an 11/23?) and there was
a Very Distant Host interface home-built by Ron Crane that ran over a copper pair to the IMP at the medical school.  I did the driver work to connect the 11/34 to the smaller 11 running the NCP.

It is kind of funny to say “smaller” when the thing you are smaller than is an 11/34.

The other thing I remember about that system is that we had a version of “ed” with an added command
that was sort of like .-10,.+10p for displaying the local context.

By the time I graduated in 1981 we had an 11/70, which was just awesome.  With the split I and D space you could programs which were (or seemed to be!) enormous.

-L

[TUHS] PDP-11 questions

[Ronald Natalie]

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> A random vaguely off-topic example: in Cambridge a PDP-11 was used as a
> terminal multiplexor for the IBM mainframe.


BRL had a PDP-11/40 that was running software called ANTS (Arpanet Terminal Server) written by the University of Illinois.   It was amusing in that it put the time on every message it printed on the terminal.   It has a “time” command that printed “is the time” (in case you didn’t know what those numbers were).    It also had silkscreened ants on the logo panels (which were orange rather than the original DEC purple and red).     The software became obsolete when the ARPANET went to long leaders.   Mike Muuss’s standard answer was to put UNIX on the machine and so it ran UNIX from December of 1980 up until the TCP/IP cutover.    I kept the ANTS logo’d racks as being kind of cool but had a hard time explaining to the Army what this $65,000 of computer equipment was I was disposing of.

The system I started on at JHU had run RSTS until Mike and friends convinced the EE department that they could get BASIC PLUS to run under UNIX on the PDP-11/45.    This turned out not too be too hard.   Despite what the processor handbook said you were supposed to use, DEC always used EMT for their system calls.    UNIX followed the guidance and used TRAP.   This made it a lot easier.

I had experience around the university running DOS/BATCH (anybody remember that phone book of a manual) and RT-11 on things like 11/20s and the original LSI-11s that really couldn’t run a full up UNIX.    I even worked on this dreadful Heathkit H-11 with it’s awful H-9 terminal (no preprinted keycaps you stuck labels to the blanks for the letters and it’s the only UPPER CASE ONLY terminal I ever saw that you had to run LCASE mode on because if you sent it lower case letters rather than just upshifting them it printed gibberish instead).

My first job after college was writing database for a government project using two connected RSX-11M systems, but we had a third system that I installed PWB UNIX on (OK well it was IS/1) and used that as our source code control system for the RSX system (we also did all our docs in nroff on the system where I had hacked the -mm macro package to handle security classifications).

When UNIX got too bloated for PDP-11s I recycled most of them into internet routers.   I did use one as an IO control processor for the Denelcor HEP system we had.   The HEP had 32 individual UNIBUSes connected to the IO memory and an 11/34 had the job of reflecting the IO requests from the HEP itself back onto those unibuses.
It ran the same “Little Operating System” that the routers did.

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[TUHS] PDP-11 questions

[Johnny Billquist]

On 2016-01-25 13:54, John Cowan wrote:
> Johnny Billquist scripsit:
>
>> The 310 was not called a Professional, though. It was the EDUsystem
>> if I remember right.
>
> I never heard of an EDUsystem built into a desk; they all predated
> the 8/A.  This was running COS-310, an offshoot of OS/8.
> See Doug Jones's PDP-8 FAQ.

COS-310 was the OS for the EDUsystem 310. As far as I can remember, it 
is not based on OS/8. I think you are right that the EDUsystem predated 
the 8/A, but they are not that far apart.

If you are thinking about the 8/A built into a desk, that was not called 
a 310 anything. You could, of course, boot COS-310 on it, though. In 
fact, the 8/A in the desk would have been the DECstation 88, or 
something like that. I need to go and dig up my old DEC handbooks to 
verify that, though. But I was amused when the "DECstation" (MIPS based) 
came out, and remembered thinking that I've seen DECstations before. :-)

I know of Doug Jones FAQ. I probably contributed to it, and I was 
definitely around before it, or Doug, had heard of PDP-8s. :-)

All that said, my memory do sometimes play tricks on me, so if I'm 
wrong, and someone can point at a DEC document that says otherwise, I'll 
happily admit my error.

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

[TUHS] PDP-11 questions

[John Cowan]

Johnny Billquist scripsit:

> The 310 was not called a Professional, though. It was the EDUsystem
> if I remember right. 

I never heard of an EDUsystem built into a desk; they all predated
the 8/A.  This was running COS-310, an offshoot of OS/8.
See Doug Jones's PDP-8 FAQ.

-- 
John Cowan          http://www.ccil.org/~cowan        cowan at ccil.org
One Word to write them all / One Access to find them,
One Excel to count them all / And thus to Windows bind them.
                --Mike Champion

[TUHS] PDP-11 questions

[Clem cole]

Dave not doubt. Sorry. I didn't  publish.  FWIW Ted took that code back to  the USG though :-).  I've forgotten when the 34 was released. I think it was late 77 maybe early 78 but it was before 79 as the 34/A would have been by then. (I'll have to ask Jeff Mitchell who did the CPU if I see him anytime soon). 


BTW Because Gordon Bell was a CMU prof , we tended to have early DEC product. Urban legend is Bell  would match transistors to make the amplifiers by hand when he designed the for runner to 8 cpu. 

We had serial #1 of the Vax and our EE dept had serial #9 of the 8 and I fairly sure the 34 was under 10 too.  My memory is that was the summer of '77.  Danny Klein and I wrote the original RK07 driver for UNIX a year later because we had a very early one of those.

  Another infamous story of CMU and early processors was the KL10 in late 75/early 76.  DEC's site prep book for the KL series had not been written and CMU wired for a KA10 not know any better.  When DEC first powered up, it blew the main circuit in Science Hall putting us all in the bldg in darkness.  I was in the computer room when it went completely silent and dark - very strange. 

Sent from my iPhone

> On Jan 25, 2016, at 12:32 AM, Warren Toomey <wkt at tuhs.org> wrote:
> 
> Implementing Unix on a PDP-11/34, Dave Horsfall, AUUGN 1(6) pg 17, September 1979, see http://www.tuhs.org/Archive/Documentation/AUUGN/AUUGN-V01.6.pdf
> Cheers, Warren
> 
>> On 25 January 2016 1:16:22 pm AEST, Dave Horsfall <dave at horsfall.org> wrote:
>>> On Sun, 24 Jan 2016, Clem Cole wrote:
>>> 
>>>  We have a very early serial # 11/34 under 10 IIRC in the EE Dept at CMU 
>>>  (One of my claims to fame was bring UNIX up on it for the first time - 
>>>  by hacking the 11/40 support - although I think Noel and few others did 
>>>  it in other places too there after).  
>> 
>> [ Warning: self-promotion ahead ]
>> 
>> I believe that I was the first to port Unix (V6) to the 11/34 in 
>> Australia; there should be a paper that I wrote, somewhere in the 
>> archives.  I was not aware of any prior work at the time, although 
>> subsequently a couple of bods came out to say that they'd beaten me to it 
>> (then why didn't they publish?).
>> 
>> In the words of the inimitable Tom Lehrer: "I publish first!".
> 
> -- 
> Sent from my Android phone with K-9 Mail. Please excuse my brevity.
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[TUHS] PDP-11 questions

[Tony Finch]

Norman Wilson <norman at oclsc.org> wrote:
>
> It worked both ways, of course.  I too suspect that a
> majority (though I'm not so sure about `vast') of PDP-11s
> never ran UNIX.

A random vaguely off-topic example: in Cambridge a PDP-11 was used as a
terminal multiplexor for the IBM mainframe.

https://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-5.pdf

Tony.
-- 
f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/
Bailey: West backing southwest, then becoming cyclonic later, 5 to 7,
occasionally gale 8. Very rough, occasionally high. Rain or wintry showers.
Good, occasionally poor.

[TUHS] PDP-11 questions

[Warren Toomey]

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Implementing Unix on a PDP-11/34, Dave Horsfall, AUUGN 1(6) pg 17, September 1979, see http://www.tuhs.org/Archive/Documentation/AUUGN/AUUGN-V01.6.pdf
Cheers, Warren

On 25 January 2016 1:16:22 pm AEST, Dave Horsfall <dave at horsfall.org> wrote:
>On Sun, 24 Jan 2016, Clem Cole wrote:
>
>> We have a very early serial # 11/34 under 10 IIRC in the EE Dept at
>CMU 
>> (One of my claims to fame was bring UNIX up on it for the first time
>- 
>> by hacking the 11/40 support - although I think Noel and few others
>did 
>> it in other places too there after).  
>
>[ Warning: self-promotion ahead ]
>
>I believe that I was the first to port Unix (V6) to the 11/34 in 
>Australia; there should be a paper that I wrote, somewhere in the 
>archives.  I was not aware of any prior work at the time, although 
>subsequently a couple of bods came out to say that they'd beaten me to
>it 
>(then why didn't they publish?).
>
>In the words of the inimitable Tom Lehrer: "I publish first!".
>
>-- 
>Dave Horsfall DTM (VK2KFU)  "Those who don't understand security will
>suffer."

-- 
Sent from my Android phone with K-9 Mail. Please excuse my brevity.
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[TUHS] PDP-11 questions

[Dave Horsfall]

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On Sun, 24 Jan 2016, Clem Cole wrote:

> We have a very early serial # 11/34 under 10 IIRC in the EE Dept at CMU 
> (One of my claims to fame was bring UNIX up on it for the first time - 
> by hacking the 11/40 support - although I think Noel and few others did 
> it in other places too there after).  

[ Warning: self-promotion ahead ]

I believe that I was the first to port Unix (V6) to the 11/34 in 
Australia; there should be a paper that I wrote, somewhere in the 
archives.  I was not aware of any prior work at the time, although 
subsequently a couple of bods came out to say that they'd beaten me to it 
(then why didn't they publish?).

In the words of the inimitable Tom Lehrer: "I publish first!".

-- 
Dave Horsfall DTM (VK2KFU)  "Those who don't understand security will suffer."

[TUHS] PDP-11 questions

[Johnny Billquist]

On 2016-01-25 02:11, John Cowan<cowan at mercury.ccil.org> wrote:
> Ronald Natalie scripsit:
>
>> >There were the Dec Professional 325 and 350 desktops which had the
>> >F-11 and the 380 had the J-11 (which should make a pretty snazzy little
>> >retro UNIX system)
> As well as the 310, which was not a desk*top* but a whole desk with a
> PDP/8-A built into it.  The first regular job I ever had was with a
> company that sold these along with their accounting software.

The 310 was not called a Professional, though. It was the EDUsystem if I 
remember right. There was also PDP-11 based EDUsystems, called 350. Not 
the same as the desktop thingy...

Isn't it wonderful how DEC reused different designations sometimes.

There was also a DECstation 88, if I remember right, which was a PDP-8 
based thing.

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

[TUHS] PDP-11 questions

[Johnny Billquist]

On 2016-01-25 02:11, jnc at mercury.lcs.mit.edu  (Noel Chiappa) wrote:
>
>      > The later M9301 (see disassembly of the contents here:
>      >http://ana-3.lcs.mit.edu/~jnc/tech/pdp11/M9301-YA.mac
>      > of one variant) didn't clear memory either
>
> OK, so_my_  memory is failing! That code does in fact test the memory.
>
> (Although, looking at it, I can't understand how it works; after writing the
> contents of R3 into the memory section it it asked to test, it complements the
> test value in R3, before comparing it with the memory it just wrote with R3,
> to make sure they are the same. Maybe there's an error in the dis-assembly?)

Read the code again, you missed it. :-)
The code first writes one value into memory (R3), then complements R3, 
and for each location checks that the memory is *not* equal to R3, and 
then writes R3 and checks that it now matches. Essentially checking that 
it can be changed into a wanted value in time. And it does it two times. 
First zeroing, and then writing ones, and then back to zeroes again, so 
yes, the memory will be left containing all zeros, except for what 
memory isn't tested.

> Anyway, it should have left the memory mostly containing all 0's.

Indeed.

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

[TUHS] PDP-11 questions

[Clem cole]

UNIX was cheap (free with a$100 tape coping fee) but processors were not as discounted as much as you might think. Yes there was a university price sheet but DEC was still making 45% gross margins on them.   And DEC was no different than its competitors

Sent from my iPhone

> On Jan 24, 2016, at 8:55 PM, David Ritchie <deritchie at yahoo.com> wrote:
> 
> But wasn't a big part of the reason that DEC was successful in academia that PDP's were pretty heavily discounted vs. commercial pricing for similar compute power? Likewise with pricing for Unix?
> 
> David Ritchie
> 
> Sent from my iPhone
> 
>> On Jan 24, 2016, at 17:40, Norman Wilson <norman at oclsc.org> wrote:
>> 
>> Noel Chiappa:
>> 
>> I'd lay good money that the vast majority of PDP-11's never ran Unix. And
>> UNIX might have happened on some other machine - it's not crucially tied to
>> the PDP-11 - in fact, the ease with which it could be used on other machines
>> was a huge part of its eventual success.
>> 
>> =======
>> 
>> I have to disagree in part: the PDP-11 is a big part of
>> what made UNIX so widespread, especially in university
>> departments, in the latter part of the 1970s.
>> 
>> That wasn't due so much to the PDP-11's technical details
>> as to its pricing.  The PDP-11 was a big sales success
>> because it was such a powerful machine, with a price that
>> individual departments could afford.  Without a platform
>> like that, I don't think UNIX would have spread nearly the
>> way it did, even before it began to appear in a significant
>> way on other architectures.  Save for the VAX, which was
>> really a PDP-11 in a gorilla suit, that didn't really happen
>> until the early 1980s anyway, and I'm not convinced it
>> would have happened had UNIX not already spread so much
>> on the PDP-11.
>> 
>> It worked both ways, of course.  I too suspect that a
>> majority (though I'm not so sure about `vast') of PDP-11s
>> never ran UNIX.  But I also suspect that a vast majority
>> of those that did might not have been purchased without
>> UNIX as a magnet.  I don't think those who weren't
>> around in the latter 1970s and early 1980s can appreciate
>> the ways in which UNIX captured many programmers and
>> sysadmins (the two were not so distinct back then!) as
>> no other competing system could.  It felt enormously
>> more efficient and more pleasant to work on and with
>> UNIX than with any of the competition, whether from DEC
>> or elsewhere.  At the very least, none of the other
>> system vendors had anything to match UNIX; and by the
>> same token, had UNIX not been there, other hardware
>> vendors' systems would have had better sales.
>> 
>> Sometime around 1981, the university department I worked
>> at, which already had a VAX-11/780 and a PDP-11/45 running
>> UNIX, wanted to get another system.  Data General tried
>> very hard to convince us to buy their VAX-competitor.
>> I remember our visiting their local office to run some
>> FORTRAN benchmarks.  The code needed some tweaking to
>> work under their OS, which DG claimed was better than
>> UNIX.  Us UNIX people had trouble restraining our chuckles
>> as we watched the DG guys, who I truly believe were experts
>> in their own OS, taking 15 or 20 minutes to do things that
>> would have taken two or three with a few shell loops and
>> ed commands.
>> 
>> DG did not get the sale.  We bought a second-hand VAX.
>> Blame UNIX.
>> 
>> Norman Wilson
>> Toronto ON

[TUHS] PDP-11 questions

[Ronald Natalie]

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> On Jan 24, 2016, at 8:55 PM, David Ritchie <deritchie at yahoo.com> wrote:
> 
> But wasn't a big part of the reason that DEC was successful in academia that PDP's were pretty heavily discounted vs. commercial pricing for similar compute power? Likewise with pricing for Unix?
> 
> David Ritchie

UNIX was effectively free for Academics and at the beginning there really wasn’t any commercial licensing.

I don’t know if DEC offered a heavy academic discount or not.   I can tell you they were cheaper than some of the options. 
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[TUHS] PDP-11 questions

[David Ritchie]

But wasn't a big part of the reason that DEC was successful in academia that PDP's were pretty heavily discounted vs. commercial pricing for similar compute power? Likewise with pricing for Unix?

David Ritchie

Sent from my iPhone

> On Jan 24, 2016, at 17:40, Norman Wilson <norman at oclsc.org> wrote:
> 
> Noel Chiappa:
> 
>  I'd lay good money that the vast majority of PDP-11's never ran Unix. And
>  UNIX might have happened on some other machine - it's not crucially tied to
>  the PDP-11 - in fact, the ease with which it could be used on other machines
>  was a huge part of its eventual success.
> 
> =======
> 
> I have to disagree in part: the PDP-11 is a big part of
> what made UNIX so widespread, especially in university
> departments, in the latter part of the 1970s.
> 
> That wasn't due so much to the PDP-11's technical details
> as to its pricing.  The PDP-11 was a big sales success
> because it was such a powerful machine, with a price that
> individual departments could afford.  Without a platform
> like that, I don't think UNIX would have spread nearly the
> way it did, even before it began to appear in a significant
> way on other architectures.  Save for the VAX, which was
> really a PDP-11 in a gorilla suit, that didn't really happen
> until the early 1980s anyway, and I'm not convinced it
> would have happened had UNIX not already spread so much
> on the PDP-11.
> 
> It worked both ways, of course.  I too suspect that a
> majority (though I'm not so sure about `vast') of PDP-11s
> never ran UNIX.  But I also suspect that a vast majority
> of those that did might not have been purchased without
> UNIX as a magnet.  I don't think those who weren't
> around in the latter 1970s and early 1980s can appreciate
> the ways in which UNIX captured many programmers and
> sysadmins (the two were not so distinct back then!) as
> no other competing system could.  It felt enormously
> more efficient and more pleasant to work on and with
> UNIX than with any of the competition, whether from DEC
> or elsewhere.  At the very least, none of the other
> system vendors had anything to match UNIX; and by the
> same token, had UNIX not been there, other hardware
> vendors' systems would have had better sales.
> 
> Sometime around 1981, the university department I worked
> at, which already had a VAX-11/780 and a PDP-11/45 running
> UNIX, wanted to get another system.  Data General tried
> very hard to convince us to buy their VAX-competitor.
> I remember our visiting their local office to run some
> FORTRAN benchmarks.  The code needed some tweaking to
> work under their OS, which DG claimed was better than
> UNIX.  Us UNIX people had trouble restraining our chuckles
> as we watched the DG guys, who I truly believe were experts
> in their own OS, taking 15 or 20 minutes to do things that
> would have taken two or three with a few shell loops and
> ed commands.
> 
> DG did not get the sale.  We bought a second-hand VAX.
> Blame UNIX.
> 
> Norman Wilson
> Toronto ON

[TUHS] PDP-11 questions

[Clem cole]

+1

Sent from my iPhone

> On Jan 24, 2016, at 8:11 PM, Noel Chiappa <jnc at mercury.lcs.mit.edu> wrote:
> 
> but I was completely blown away that
> anyone could get that much capability into a PDP-11 OS.

[TUHS] PDP-11 questions

[Noel Chiappa]

    > From: Norman Wilson

    > I have to disagree in part

You make a number of good points. A few comments:

    > the PDP-11 is a big part of what made UNIX so widespread, especially in
    > university departments

That last part was really a big factor, one not to be understated.  That
penetration led to production of a whole generation of people who i) were
familiar with Unix, and ii) liked it, and were not about to put up with the
OS's being turned out by various vendors.

    > I too suspect that a majority (though I'm not so sure about `vast') of
    > PDP-11s never ran UNIX.

'Embedded systems'. The number of PDP-11's running timesharing was a small
share of the total number, I expect.

    > I don't think those who weren't around in the latter 1970s and early
    > 1980s can appreciate the ways in which UNIX captured many programmers
    > ... as no other competing system could.

Very true. My jaw basically hit the floor when I first saw (ca. '75) what Unix
was like. People who didn't live through that transition can't _really_ grok
it, any more than my kids can really fully grok a world without mobile
phones. It wasn't as powerful as Multics, but I was completely blown away that
anyone could get that much capability into a PDP-11 OS.

     Noel

[TUHS] PDP-11 questions

[Clem cole]

Actually the important observation Christiansen makes in the book that is often missed is that the new technology when compared to the old technology is not as good by the definitions made by the market for the original.  (As the original question was raised. How did these crappy 8 bit micros best the PDP11). 

But what happens is that a new set of customers that don't care that's it a lessor item  -  find the new scheme is good enough for them and actually solves the problem they have well.   And is more economical for them. 

So If the new technology has a faster growth curve it will catch up and "disrupt" the incumbent at some point - usually while the incumbent is not realizing it - because as Steve points out, they are focusing on making what the current customers desire - which are overkill (and not economical) for the new market/customer base. 

Ie. What DEC did to IBM.  What the workstation guys did to DEC.  What the PC did to the workstation guys (an open question is the mobile doing that to the PC now- time will tell) . 

Steve you are right and. I Agree that  it is a quick and fun read and all technologist /systems folk should read it and I believe you will say "Ah ha," laugh, and learn something too. 

Clem

Sent from my iPhone

> On Jan 24, 2016, at 7:11 PM, scj at yaccman.com wrote:
> 
>  In part, it's because customers, for the most part,
> want more of the same and cheaper -- the interesting new niches get
> overlooked by the current big guys.

[TUHS] PDP-11 questions

[Ronald Natalie]

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I worked for Unipress for a brief period and learned portability from them.   I spent a lot of time moving EMACS from Suns (both 68x SUN 3’s to SPARC SUN 4), SGI, Intergraph, and Masscomp, along with some of the minicomputers (Pyramid, Vaxes, Gould SEL).    When I started my own company we ran on Sparcs of various flavors, x86 of various flavors, SGIs, Stellar, Ardent, Oxi (i860), IBM RS/6000, IBM i860, (I think I actually ported once to the 370 running AIX while I was at PASC, but we never really supported that), MIPS, DEC SPIM boxes, Alphas, and a Cray XMP and then some wierd stuff (ARPA hypercubes, Masspars, etc…).


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[TUHS] PDP-11 questions

[scj]

>     >> It seems though that there should have been a PDP-11 based desktop
>
>     > Because DEC were a bunch of losers.
>
>
> Why not? I put it down to corporate cultural intertia - ironically, the
> same
> thing that allowed DEC to eat so much of IBM's lunch.
>

Also see the book "The Innovator's Dilemma".  I takes a very insightful
look at why the leader of one generation of technology is rarely the
leader of the next.  In part, it's because customers, for the most part,
want more of the same and cheaper -- the interesting new niches get
overlooked by the current big guys.

Besides, the book is worth reading for a hilarious picture of how the
steam shovel makers tried to make a backhoe to compete with the hydraulic
technology that was eating their lunch...

Steve

[TUHS] PDP-11 questions

[Norman Wilson]

Noel Chiappa:

  I'd lay good money that the vast majority of PDP-11's never ran Unix. And
  UNIX might have happened on some other machine - it's not crucially tied to
  the PDP-11 - in fact, the ease with which it could be used on other machines
  was a huge part of its eventual success.

=======

I have to disagree in part: the PDP-11 is a big part of
what made UNIX so widespread, especially in university
departments, in the latter part of the 1970s.

That wasn't due so much to the PDP-11's technical details
as to its pricing.  The PDP-11 was a big sales success
because it was such a powerful machine, with a price that
individual departments could afford.  Without a platform
like that, I don't think UNIX would have spread nearly the
way it did, even before it began to appear in a significant
way on other architectures.  Save for the VAX, which was
really a PDP-11 in a gorilla suit, that didn't really happen
until the early 1980s anyway, and I'm not convinced it
would have happened had UNIX not already spread so much
on the PDP-11.

It worked both ways, of course.  I too suspect that a
majority (though I'm not so sure about `vast') of PDP-11s
never ran UNIX.  But I also suspect that a vast majority
of those that did might not have been purchased without
UNIX as a magnet.  I don't think those who weren't
around in the latter 1970s and early 1980s can appreciate
the ways in which UNIX captured many programmers and
sysadmins (the two were not so distinct back then!) as
no other competing system could.  It felt enormously
more efficient and more pleasant to work on and with
UNIX than with any of the competition, whether from DEC
or elsewhere.  At the very least, none of the other
system vendors had anything to match UNIX; and by the
same token, had UNIX not been there, other hardware
vendors' systems would have had better sales.

Sometime around 1981, the university department I worked
at, which already had a VAX-11/780 and a PDP-11/45 running
UNIX, wanted to get another system.  Data General tried
very hard to convince us to buy their VAX-competitor.
I remember our visiting their local office to run some
FORTRAN benchmarks.  The code needed some tweaking to
work under their OS, which DG claimed was better than
UNIX.  Us UNIX people had trouble restraining our chuckles
as we watched the DG guys, who I truly believe were experts
in their own OS, taking 15 or 20 minutes to do things that
would have taken two or three with a few shell loops and
ed commands.

DG did not get the sale.  We bought a second-hand VAX.
Blame UNIX.

Norman Wilson
Toronto ON

[TUHS] PDP-11 questions

[Norman Wilson]

Clem Cole:

  Also by the time DEC did try to build a workstation (after Masscomp,
  Apollo, Sun et al had taken many of their engineers) it was too little too
  late.   The ship had sailed and they never recovered that market.

======

There was a window in the early 1990s when I think they could
have recovered.  DEC had some pretty good MIPS-based workstations,
and Alpha was just coming out and was even better.  Ultrix was
a good, solid system, and DEC OSF/1 (later Digital UNIX) was
getting there.

In 1994 or so, the group I worked in needed a new workgroup-sized
central server.  Our existing stuff was mostly DECstations running
Ultrix (with a few SGI IRIX systems for specialized graphics).
We looked at the price and performance of various options:
everything SGI had was too pricey; Sun's was well behind in
performance (this was before UltraSPARC), and their OS was
primitive and required a lot of retrofitting to be usable
(this was also before Solaris 2 even came out, let alone
became stable; also before Sun grew up enough to ship a
decent X11 as part of the system).

So we bought a third-party system with an Alpha motherboard
in a PC-style case.  In burn-in testing I discovered a bug in
the motherboard; the vendor were happy to fix it once they
could reproduce it in their lab (which took some doing, but
that was another story).

We were quite happy with that system, and would have bought
more had our entire department not been shut down in a
mostly-political fuss a couple of years later (that too is
another story).

DEC's desktop MIPS systems were quite good, and the Alpha
followons even better.  Had the company's upper management
not by then lost all sense of how to run a company or to
sell anything ... but that was not to be.

Old-fart footnote: when our department shut down, I bought
some of our DECstations cheap from the university.  I still
have them on a shelf downstairs; I've never done much with
them.

Norman Wilson
Toronto ON

[TUHS] PDP-11 questions

[John Cowan]

Ronald Natalie scripsit:

> There were the Dec Professional 325 and 350 desktops which had the
> F-11 and the 380 had the J-11 (which should make a pretty snazzy little
> retro UNIX system)

As well as the 310, which was not a desk*top* but a whole desk with a
PDP/8-A built into it.  The first regular job I ever had was with a
company that sold these along with their accounting software.

I got involved when they switched to developing for the PDP-11, writing
in Dibol and PDP-11 assembler.

-- 
John Cowan          http://www.ccil.org/~cowan        cowan at ccil.org
But you, Wormtongue, you have done what you could for your true master.  Some
reward you have earned at least.  Yet Saruman is apt to overlook his bargains.
I should advise you to go quickly and remind him, lest he forget your faithful
service.  --Gandalf

[TUHS] PDP-11 questions

[Clem Cole]

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​below​

On Sun, Jan 24, 2016 at 12:37 PM, Mark Longridge <cubexyz at gmail.com> wrote:

> Ok, I got a few questions about PDP-11.
>
> First, I was wondering when Bell Labs got that first PDP-11/20 what
> software (if any) came with it? I assume when one bought a PDP-11/20
> you would get some type of OS with it.
>
​SW?? We don't need no stinking SW - we do our own..

Seriously, SW was an option you paid for. The system came with paper tapes
to run diagnostics to prove the system worked.   And when they got their
first 11, there is no disk and DOS-11( it's 1st OS) was not yet released
IIRC.  ​

Have to ask Ken, but my guess and I think one or more of the BLTJ articles
back it up, the would have purchased it as it.   Maybe an standalone
assembler running from paper tape or DEC tape.  But whatever it had, it
would have been very, very limited.

But that was not an issue, they had other systems and could write their own
tools and cross assemble or compile them as needed (which is what they
did).




> According to the folks at alt.sys.pdp11 the PDP-11 computer doesn't
> have anything equivalent to a PC's BIOS.
>
​Sigh... Kids these days .... more in a minute....​




> ​... ​
> Wouldn't the DRAM
> ​ ​
> on the PDP-11/something need to be initialized too?
>
​What's DRAM -- early 11's had core.   That said, Intel was selling the
1101 (1k x1 bit) chips which were being consumed at a pretty good rate for
the memory systems for PDP-10s​.    DEC would not release a DRAM board for
the 11 for a few more years.   It was 2K x 16 bits (with ECC IIRC).    And
they were pretty pricy.   I seem to remember the had faster access times
that the core boards, but I'm hazy on that.

When UNIX starts to leak to the Universities in the mid to late 70's many
(??most??) of us are using DRAM on our 11's but we would often by the
minimum config from DEC and the use after market DRAM boards.   We have a
very early serial # 11/34 under 10 IIRC in the EE Dept at CMU (One of my
claims to fame was bring UNIX up on it for the first time - by hacking the
11/40 support - although I think Noel and few others did it in other places
too there after).

Anyway - that system had 24K words (48K bytes) of DRAM memory on it to
start with.  We made some memory board for it ourselves to max it to 128K
words and National Semi memory chips.   I remember the value of the memory
chips was greater than the CPU at that point.

​Anyway - core machine you did not want to init.  You usually left the OS
or whatever in place.
It's going to be interesting to see if this becomes the new norm with the
Crystal Ridge (Xpoint 3D or whatever marketing is calling it).


Perhaps an older
> PDP-11 doesn't have DRAM but surely the later models did?
>
Sure by why the pre-boot have to do it?  Init of the memory system is done
by the OS.   Look at the code in V6 and V7 that is called very early and
prints out the size of the memory it finds.   It's working backwards until
it find memory that responds and clears it out.

There are a few parts/functions to the BIOS rooms and fear you may be
mashing the together.
Init of the memory system is not done in the original PC BIOS the way it is
done now.  There reason is because today we have memory controller chips
with lots and lots of different options.
The firmware BIOS is used to set up that controller (pre-boot).   The 11
(and the Vax for that matter) did not have such an idea.   What we call the
memory controller was just part of the logic in the CPU.
​


> ​... ​
> It
> ​ ​
> seems though that there should have been a PDP-11 based desktop and as
> far as I can tell that didn't happen. Instead we got a bunch of micros
> with 8080, z80 and 6502 cpus, but nothing that could run Unix, at
> least not a Unix v7 with source code.
>
​I can see from an later observers view you might fall into a trap thinking
this, but a bunch of it is actually not true.

1)  There were small form factor PDP-11's that did appear late in the
PDP-11's life.   Some based on the LSI-11 and some even on the F-11/J-11
(single chip 11).   DEC had a line called DEC Processional series.  But
they really were not super popular.  But as other point out, DEC was slow
to recognize this as a market. In fact a professor at Harvard business
explain the problem at DEC and coins a term for the behavior when the 8 bit
and 16 bit micros appear [Clay Christiansen's book "The Innovators'
Dilemma" - the term is call "disruptive technology."]

FWIW:  At this time, Wang Labs (Dr. Wang invented the core memory at IBM
BTW, was selling a system for secretaries / admin that ran originally on an
8080, later a Z80.   It was quite popular for what it could do... which was
allow them to edit letters/documents.   But it was very much focused on a
specific market/task - which interestingly enough was the original task
UNIX had ;-)

Also by the time DEC did try to build a workstation (after Masscomp,
Apollo, Sun et al had taken many of their engineers) it was too little too
late.   The ship had sailed and they never recovered that market.

2) Economics was really the reason.  Please understand in the 1975 dollars,
a 11/34 with 2 RK05's, 24K words of memory and a single serial interface
cost about $45K.​    If you want to a 9-track tape drive that was another
4-8K, 200M RPxx style disk, another $15K, as I said the chips to make the
memory was $45K.  Much less, serial ports, a printer etc....

Using an 11 for "personal" computer was not cost effective.   You would
need to get the prices of memory, large storage, down and size/speed of the
processors in single chip form before you really do it.

That said with birth of the IBM PC, Andy Tannebaum wrote a really good Unix
V7 clone for the 16 bit 8088 - called Minux.   And V& itself began to move
to more capable micro's    But DEC was making a huge amount of money
selling Vaxen.   So the workstations and small capability systems were not
interesting (see Christiansen for why).

3)  Some people actually did get UNIX or close to unix functionality
running on the 8-bit machines.  The Guy who wrote BDS C (Brain Damaged
Software) brought an 8" floppy disk based Z80 system that originally had
been running CP/M to a Usenix in the late 1970's/early 1980s and showed a
couple of us including Dennis his OS.   I remember Dennis being pretty
impressed and stating that was it was fast and as good as he remember early
UNIX.   He was quite encouraging.
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[TUHS] PDP-11 questions

[Ronald Natalie]

There were the Dec Professional 325 and 350 desktops which had the F-11 and the 380 had the J-11 (which should make a pretty snazzy little retro UNIX system)

.
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[TUHS] PDP-11 questions

[Johnny Billquist]

On 2016-01-24 19:01, Mark Longridge<cubexyz at gmail.com> wrote:
> Ok, I got a few questions about PDP-11.
>
> First, I was wondering when Bell Labs got that first PDP-11/20 what
> software (if any) came with it? I assume when one bought a PDP-11/20
> you would get some type of OS with it.

No. You might get diagnostics, but any kind of OS you would have to buy 
separately, and there were several to choose from, depending on your needs.

> According to the folks at alt.sys.pdp11 the PDP-11 computer doesn't
> have anything equivalent to a PC's BIOS. But I know a bit about what a
> PC's BIOS does and that includes RAM Initialization. Wouldn't the DRAM
> on the PDP-11/something need to be initialized too? Perhaps an older
> PDP-11 doesn't have DRAM but surely the later models did?

RAM don't need to be initialized. Maybe you mean clearing it, so it 
don't contain random information?

ECC memory, on the other hand needs to be initialized, but for those 
PDP-11s who has that, the initialization is done in hardware.

> Now the last question has to do with what made the PDP-11 architecture
> so great. Part of that had to be the relatively affordablility of the
> PDP-11 and of course it was the machine that made Unix possible. It
> seems though that there should have been a PDP-11 based desktop and as
> far as I can tell that didn't happen. Instead we got a bunch of micros
> with 8080, z80 and 6502 cpus, but nothing that could run Unix, at
> least not a Unix v7 with source code.

The architecture is very easy to program on, and rather intuitive. You 
have general registers, an orthogonal instruction set, and the machine 
can be programmed as a stack based, a register based, or just plain 
memory-to-memory style equally well.

In addition, I/O is pretty simple, as there are no special I/O 
instructions. Same instructions as for anything else are also used for I/O.

Also, the memory model on the PDP-11 is pretty nice, with a proper MMU 
which allows you to write reasonable OSes.

There were in fact desktop based PDP-11s, but DEC shot themselves in the 
foot there. They were afraid of eating into their own business, so they 
made the desktop PDP-11 incompatible in some ways with all other 
PDP-11s, so you could in general not run much PDP-11 software on the 
desktop, but had to develop specific programs for that platform. That, 
and the fact that it took DEC too long to enter the market, meant that 
the IBM PC had already become the standard by the time DEC came with the 
Professional (the PDP-11 desktop).

DEC also made a couple of other PDP-11 based systems that were sortof 
desktop, such as the VT-103, which was a VT100 with a PDP-11 inside. 
Interesting idea, but the VT103 didn't have good mass storage, and had a 
very slow and limited PDP-11 CPU. The PDT-11 was another attempt, with 
similar issues as the VT-103.

If we were to examine prototype things, DEC did a lot more as well, 
including a portable PDP-11 with an LCD display. Never became a product.

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

[TUHS] PDP-11 questions

[Noel Chiappa]

    >> It seems though that there should have been a PDP-11 based desktop

    > Because DEC were a bunch of losers.

OK, that was kind of harsh. (Trying to send email too fast...) DEC had a lot
of really brilliant people, and they produced some awesome machines.

But when it comes to desktops, I think there is a certain amount of
bottom-line truth in that assessment: there was a huge market there
(obviously), and DEC should have been in a pretty good place to capture it,
but it completely failed to do so.

Why not? I put it down to corporate cultural intertia - ironically, the same
thing that allowed DEC to eat so much of IBM's lunch.

Just as IBM took way too long to understand that there was a very large
ecological niche for smaller machines _with customers who didn't want or need
the whole IBM hand-holding routine_, DEC never (or, at least, until way too
late to catch the wave) could change their mentality from producing really,
really well built computers for people who were all technical, to commodity
computers which needed to be made as absolutely cheaply as possible, and for
people who were non-technical.

The company as a whole just couldn't change its mindset that radically, that
quickly. (And a lot of the blame for that has to go to Ken Olsen, of course.
He just didn't grok how the world was changing.)

    > There's some DEC history book which talks about DEC's multiple failures
    > (on a variety of platforms, not just PDP-11 based ones) to get into the
    > desktop market, if the title comes to me, I'll post it.

The best one on this topis, probably, is "Ultimate Entrepreneur", by Glenn
Rifkin and George Harrar, which gives a lot of detail on DEC's attempts to
build personal computers; also good is "DEC is Dead, Long Live DEC", by Edgar
Schein.

	Noel

[TUHS] PDP-11 questions

[Noel Chiappa]

    > From: Mark Longridge

    > when Bell Labs got that first PDP-11/20 what software (if any) came
    > with it?

I have this bit set that they didn't get anything, they wrote a
cross-assembler on another machine. I know that when it came, it didn't have a
disk (wasn't ready yet), so it ran a chess problem (memory only) for quite a
while until the disk came. I think that's in the ACM paper, or if not, one of
the BSTJ Unix history papers.


    > Perhaps an older PDP-11 doesn't have DRAM but surely the later models
    > did?

MOS memory came in starting roughly around the time of the 11/04 and /34.
(Well, that's not quire right - there were bipolar and MOS memory options
for the 11/45, the second PDP-11 model, but they were kind of special.)

But the earliest ROM bootstraps were too small to have space for code to
clear memory, or anything like that. The diode-array BM792 ROM certainly
didn't.

The later M9301 (see disassembly of the contents here:

  http://ana-3.lcs.mit.edu/~jnc/tech/pdp11/M9301-YA.mac

of one variant) didn't clear memory either, although there was probably room
in the ROMs by that point.

I suspect it didn't because nobody bothered with stuff like that back then -
you just wrote over whatever was already there. Properly written code would
never have referenced a location which had not been loaded or written to, that
way you couldn't get a parity error from random gubbish in semi-conductor at
power up (and of course core always had old data in it).


    > Now the last question has to do with what made the PDP-11 architecture
    > so great.

Bang/buck (in the metaphorical sense) ratio.

For a machine with a 16-bit word size (i.e. limited instruction size), it had
remarkable programming capability. Data could be in registers, pushed or
popped with a stack, at fixed addresses, PC-relative, indexed into a table,
etc, etc. And _all_ the instructions (basically) had acceess to _all_ those
modes.

As a result, the code density was probably higher than any similar sized
machine, and back when memory was core (i.e. expensive/limited), code density
was important.

The bus was also extremely flexible, given how simple it was: memory and
devices were all on the same (simple) bus.

    > of course it was the machine that made Unix possible

I'd lay good money that the vast majority of PDP-11's never ran Unix. And
UNIX might have happened on some other machine - it's not crucially tied to
the PDP-11 - in fact, the ease with which it could be used on other machines
was a huge part of its eventual success.

    > It seems though that there should have been a PDP-11 based desktop and
    > as far as I can tell that didn't happen.

Because DEC were a bunch of losers. There's some DEC history book which talks
about DEC's multiple failures (on a variety of platforms, not just PDP-11
based ones) to get into the desktop market, if the title comes to me, I'll
post it.

	Noel

[TUHS] PDP-11 questions

[Mark Longridge]

Ok, I got a few questions about PDP-11.

First, I was wondering when Bell Labs got that first PDP-11/20 what
software (if any) came with it? I assume when one bought a PDP-11/20
you would get some type of OS with it.

According to the folks at alt.sys.pdp11 the PDP-11 computer doesn't
have anything equivalent to a PC's BIOS. But I know a bit about what a
PC's BIOS does and that includes RAM Initialization. Wouldn't the DRAM
on the PDP-11/something need to be initialized too? Perhaps an older
PDP-11 doesn't have DRAM but surely the later models did?

Now the last question has to do with what made the PDP-11 architecture
so great. Part of that had to be the relatively affordablility of the
PDP-11 and of course it was the machine that made Unix possible. It
seems though that there should have been a PDP-11 based desktop and as
far as I can tell that didn't happen. Instead we got a bunch of micros
with 8080, z80 and 6502 cpus, but nothing that could run Unix, at
least not a Unix v7 with source code.

Mark