> Thank you for responding so carefully.
The devil is in the details...
> I have been reading the PDP-11/40 handbook, much too much :)
I'm not sure that's possible! :-)
Yes, yes, I know, the architecture is deader than a doornail for serious use,
but I liken it to sailing vessels: nobody uses them for serious cargo haul any
more, but they are still much beloved (and for good reasons, IMO).
The PDP-11 is an incredibly elegant architecture, perhaps the best ever (IMO),
which remains one of the very best examples ever of how to get 30 pounds into
the proverbial ten-pount sack - like early UNIX (more below).
> this is really elegant code. The guys who thought this up were amazing.
Nah, it's just a clever hack (small-scale). What is really, almost
un-approachably, brilliant about early UNIX is the amount of functionality
they got into such a small machine.
It's hard to really appreciate, now, the impact UNIX had when it first
appeared on the scene: just as it's impossible for people who didn't
themselves actually experience the pre-Internet world to _really_ appreciate
what it was like (even turning off all one's computers for a day only
approximates it). I think only people who lived with prior 'small computer
OS's' could really grasp what a giant leap it was, compared to what came
I remember first being shown it in circa 1975 or so, and just being utterly
blown away: the ability to trivially add arbitrary commands, I/O redirection,
invisibly mountable sections of the directory tree - the list just goes on and
on. Heck, it was better than all but a few 'big machine' OS's!
> Thanks again for your help.
Eh, de nada.
Well, of course there are conferences and there are conferences. The
only conference I've ever had a paper published at, Balisage, is as
peer-reviewed as any journal. (And it is gold open access and doesn't
charge for pages -- the storage costs are absorbed as conference overhead.)
Have you actually looked up the cited reference?
The trouble is not that it's a conference paper. The trouble is
that that the `authority' being cited is just a random assertion,
not backed up.
It's as if I mentioned your name in a paper about something else,
remarked in passing and without any citation of my own that you have
a wooden leg, and Wikipedia accepted that as proof of your prosthesis.
(Four limbs and eight eyes, thank you very much)
On Dec 22, 2015, at 5:44 PM, Norman Wilson <norman(a)oclsc.org> wrote:
> If that's the quality of reference they accept, there is simply no
> reason to take anything they publish as gospel.
You're mistaking Wikipedia for an information source you can rely on. It's
not. It's more akin to an attempt to prove that an infinite number of
monkeys, with an infinite number of typewriters, and an infinite amount of
time, can produce a reliable encyclopaedia.
(Yes, yes, spare me the surveys that show that Wikipedia's error rates aren't
that bad, when compared with other encyclopaedias, etc.)
Don't get me wrong, Wikipedia is quite useful as a place for an
_introduction_ to any topic, but anyone who really wants to _reliably_ know
anything about a topic needs to look at the references, not the articles.
There was an attempt to do a Wikipedia-like online encyclopaedia that one
could rely on - Citizendium - but alas it doesn't seem to have taken off (or
hadn't when I got distracted from working on it).
And I know whereof I speak; those who wish to be amused may want to read:
And apologies for continuing the off-topic (this group certainly can't fix
Wikipedia, people have been complaining about this problem for many years
now), but some buttons, you just have to respond when they are pushed...
On 2015-12-23 17:04, norman(a)oclsc.org (Norman Wilson) wrote:
> John Cowan:
> Wikipedia is by nature a*summary of the published literature*. If you
> want to get some folklore, like what "cron" stands for, into Wikipedia,
> then publish a folklore article in a journal, book, or similar reputable
> publication. Random uncontrolled mailing lists simply do not count.
> That sounds fair enough on the surface.
> But if you follow the references cited to support the cron
> acronyms, you find that random unsupported assertions in
> conference papers do count. That's not a lot better.
I've had similar experiences with Wikipedia in the past. At one point I
was trying to get the PDP-11 article corrected, as it said that the
PDP-11 was an architecture that disappeared in the 80s (paraphrasing). I
pointed out that the last *new* PDP-11 model from DEC itself was
released in 1990, and that others are still making new PDP-11 CPUs.
My corrections were reverted, and I was asked for citations. I went
through a silly loop of requests for sources for my claims, while there
seems to have been no demand for citation for the original claims, more
than the "knowledge" of someone. It wasn't until I dug up the system
manuals and documentation from DEC about the PDP-11/93 and PDP-11/94
(which have actual time of original publishing date printed) that my
claims were (somewhat) accepted.
I've also had numerous fights about the Wikipedia articles about virtual
memory, where the original authors on the article clearly had not
understood the difference between virtual memory and demand paged
memory. The articles are better today, but when I last looked, they
still had some details wrong in there. And getting anything corrected is
hell, as any silly statement that is already in is almost regarded as
gospel, and anything you try to correct is questioned to hell and back
before anyone will accept it. (Hey, according to Wikipedia, a PDP-11 do
not have virtual memory... I wonder what it has then. Fake memory?
Although, the article might now actually accept that a PDP-11 do have
virtual memory, although no OS I know of implements demand paging, but
that could be done as well, if anyone wanted to.)
Nowadays, I use Wikipedia to find information, but just take everything
in there with a large grain of salt when it comes to details. There are
just too many ignorant people who are writing stuff, and who seem to get
anything accepted, and too much hassle to get anything corrected when
you actually knows the subject.
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt(a)softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
Perhaps Wikipedia would be satisfied if we could get
Ken to write a letter to some current published journal,
saying that he's the one who named cron, he's heard
people are interested in how it got that name, here's
how. We could then cite that as a reference.
On the other hand, this may be an example of the
degree to which one should trust Wikipedia. The
`command run on notice' acronym claim is backed up
by an article from the AUUG (Hi Warren!) Proceedings,
1994, in which the first reference to cron gives
that explanation with no further reference.
If that's the quality of reference they accept, there
is simply no reason to take anything they publish
as gospel. Sorry.
Proud that no one has yet made a spurious Wikipedia
page asserting the etymology of my personal domain
As a guy who has donated money to Wikipedia this whole thread makes
me not want to donate again. Just me being grumpy.
Perhaps we should start our own online encyclopedia.
In the Ken tradition we could call it pedi.
(pdia sounds better, but pdia.org is already taken.)
I had never doubted that "cron" was a contraction of "chrono-".
Wikipedia, however, offered several folk acronyms on a par
with it. Brian asked Ken, who confirmed,
"cron comes from the prefix (greek?) for time.
it should have been chron, but i never could spell."
I edited Wikipedia to expunge the nonsense. Amusingly that
makes the article less "verifiable" because there had been
literature citations for the nonsense, but there is none
for the fact.
I am in the process of gaining a deeper understanding of PDP-11 machine
instructions and how the bootstrap loader and its cousins function. As
part of that process, I am analyzing the code. I am concurrently working
through the DEC bootstrap loader and the bootstrap loader that is
described in the v6 documentation. The DEC bootstrap loader, while
fascinating and elegant, is relatively straightforward, given its
enormous range and the fact that it is self-modifying. I wrote up my
preliminary notes here:
The code that is in the v6 documentation on the other hand is not
yielding easily to reasonable interpretation and I was hoping y'all
might be able to shed some light on how it works.
The following is the TU10 (TM11) bootstrap code from "Setting Up Unix -
The author's notes around the code are:
The tape should move and the CPU loop. (The TU10 code is not the DEC
bulk ROM for tape; it reads block 0, not block 1.)
Halt and restart the CPU at 0. The tape should rewind. The console
should type ‘=’.
Of course, following the instructions results in a successful outcome,
but understanding what is happening is difficult given that this is a
virtual environment and no discernible tape movement can be detected.
My attempt at interpretation is along the following lines, I
manufactured the dissasembly based on my reading of the PDP-11/40
handbook and the machine codes:
012700 MOV #172526, R0 ; moves the TM11 Current Memory Address Register
(MTCMA) address into R0
172526 ; the immediate operand
010040 MOV R0,-(R0) ; moves the contents of R0, 172526, into
memory location 172524, the TM11 Byte Record Counter (MTBRC)
012740 MOV #60003,-(R0); moves 60003 into memory location 172522, the
TM11 Command Register (MTC)
060003 ; immediate data
This seems like gobbledegook to me. It moves the MTCMA (Magtape Current
Memory Address) into R0, then it moves the MTCMA into the MTBRC (Magtape
Byte Record Count), then it moves 60003 into the MTC (Magtape control
register), which causes a read operation with 800BPI 9 Channel density.
172526 is -5252 in 2's complement.
Am I misinterpreting the byte codes or is this some idiosyncratic way to
get the Magnetic tape to rewind or something (the TM11 has a control
function to rewind, so it seems unlikely that this is the case, but I'm
I single stepped through the code in the simulator, and the TM11
registers appear to be pretty unobservable (examining these three
registers always displays 0's, but if I change from referencing the TM11
registers to another area of memory, say 100500 I see the values I would
expect to see as they are being moved from the registers into memory).
Ok, not sure if anyone will want to do this but I've just compiled
ed.c from Unix v6 on Unix v5.
It's not much bigger than the assembled ed, with 1314 lines of C code
the compiled executable is only 6518 bytes vs 4292 for the original. I
was looking at the source code and didn't see anything that the v5 cc
couldn't handle. I trimmed the source a bit, there's a function at the
end called getpid() which is commented out.
The comment says:
/* Get process ID routine if system call is unavailable. */
but my version of v5 does have that system call so it's all good.
It's been run a few times and it seems to work just fine. It may even
have a few more features than the v5 ed, I'm not sure yet :)