Subject: PDP-8's?

From: [email-masked] (David Turner)
Date: Sat, 11 Sep 93 00:19:00 -0500

Greetings!

I just now found this conference and was wondering if anyone really has
any PDP-8 stuff/information? Is there sort of like a PDP-8 fan club? :)

I once had a PDP-8/e but had to get rid of it when I moved. :(
I still have several of the books, tho.

Lets see a show of hands out there... What is everyone up to?

Regards,
** David Turner **

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 þ QMPro 1.0 00-0000 þ Misspelled?  Impossible.  My modem is error correcting.

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From: [email-masked] (Johnny Billquist)
Date: 12 Sep 93 11:31:35 GMT

>Greetings!

Hi.

>any PDP-8 stuff/information? Is there sort of like a PDP-8 fan club? :)

Well, I got seven pdp-8 myself. One 8/e, one 8/f, two 8/m, and three 8/a.
I'm actually typing this using one of my 8/a. :-)
There are more of us out there than you might suspect at first glance.
Apart from this newsgroup, there is the pdp8 mailinglist:
[email-masked]
But both that list, and this group is pretty quiet most of the time.
I guess we're having a hard time to come up with subjects to talk about.
The only things I can think of straight away is swapping hardware and
software. I think I have put up a few pieces of software on ftp.update.uu.se
for people to grab. I have lots of more, but transfering it with kermit takes
some time, which I as usual don't have. However, if enough interest exists,
I can put up a lot of stuff there.

>I once had a PDP-8/e but had to get rid of it when I moved. :(

Too bad. :-(

>I still have several of the books, tho.

Me too.

>Lets see a show of hands out there... What is everyone up to?

Here is one hand.
What I'm up to? Well, apart from keeping one pdp8 in my student room (the
rest is by my parents), I'm keeping two pdp-11/70 alive and running.
About to get a VAX8650 up and running as well. I'd like to find a large
place to live, where I could get my bigger pdp8-system up and running.
I don't do anything special on my pdp8 at the moment.
(Except for using it every day...)

--
Johnny Billquist                  || "I'm on a bus
CS student at Uppsala University  ||  on a psychedelic trip
email: [email-masked]       ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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From: [email-masked] (David Turner)
Date: 13 Sep 93 03:47:00 GMT

B>>I just now found this conference and was wondering if anyone really has
 >>any PDP-8 stuff/information? Is there sort of like a PDP-8 fan club? :)

B>Well, I got seven pdp-8 myself. One 8/e, one 8/f, two 8/m, and three 8/a.
 >I'm actually typing this using one of my 8/a. :-)

Wow. You sure have (had) me beat. I thought I was one of the last people
in the world to have one. I had a PDP-8/e and an 8/m. Everything was
dead, and we (me and my friend) brought it back to life. Very neat.
Almost died laughing when the date program wouldn't go past 1976! (I
think). Had it up and running OS/8 on diskettes. I also used to use the
big rack mounted 8/e to heat my bedroom. ;) Does anyone have an old
PDP-8 they would like to give to a good home?

B>Here is one hand.
 >(Except for using it every day...)

Wow again. You must have very understanding parents! Just curious, where
do you live? I am not too up on signatures and geography... :)

Regards, ** David Turner **

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 ~ QMPro 1.0 00-0000 ~ Dogs come when you call. Cats have answering machines.

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From: [email-masked] (Johnny Billquist)
Date: 16 Sep 93 23:10:03 GMT

>dead, and we (me and my friend) brought it back to life. Very neat.

Well, there are quite a few other people around here who has pdp8's up
and running.

>PDP-8 they would like to give to a good home?

Hmmm, you must have had an old version of OS/8. It was modified to take
dates until 1999. (Some strange effects can be noted from that patch,
but that is another story...)

>do you live? I am not too up on signatures and geography... :)

Well, the pdp-11s and the VAX is not by my parents, only the rest of my
pdp8's are.
The rest of the stuff is at the university here, owned by the computer
club here, with me as chairman and one of the most active members.
I'm slowly building up an ftp archive of DEC stuff by the way. Have
a few OS/8 items there as well. Look at ftp.update.uu.se

I live in Uppsala, Sweden. My parents are in Stockholm.

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From: [email-masked] (Charles Lasner)
Date: 19 Sep 1993 01:21:23 GMT

In article <bqt.748221003@Minsk>,

>but that is another story...)

Back in the days before OS/8 V3D, the date was only good from 1970-1977, since
the OS/8 date format, which was hastily designed, only allocates three bits
for the year.

As of V3D, the format was "enhanced" in a kludged way:

There are two bits in memory (in 07777) that affect the base year to be
either 1970, 1978, 1986, or 1994.  So, the current year is the value of the
two bits times eight plus the current year offset.  Thus the year (in theory)
now runs from 1970-2001.  However, there are several problems with this
implementation:

a)	Most programs can't format out the year past 1999 due to the use of
	limited range arithmetic methods.  This means that 2000 and 2001 get
	junk and non-digits in the output.  Some are even just two digit
	routines to append onto a constant "19".  OS/8 is not the first, nor
	the last, to have this problem!

b)	The existent routines to set the date can't parse input for 2000 and
	2001.  This can be corrected within OS/8 itself, but only extends the
	usefulness of the lifetime of the date for another two years.

c)	The worst problem - the date is anomolous!  The common implementation
	of the date for virtually all files is to only store the three bits
	that merely define the date offset, not the absolute date!  Thus, all
	systems "guess" at the date in terms of the current year.  A file
	*must* be presumed to exist in the current year or at most the previous
	seven years.  Note that at the beginning of the year, most files that
	seem to be in the nearby future are more likely eight years old!  (Or
	multiples of eight years old!)  This could be marginally corrected to
	check to see if the file's date is in the future of the apparent
	current year, and if so, at least proclaim it to be eight years old.
	This would be more helpful in January than December, but adds a drop
	in the bucket, etc.

When OS/8 was formulated, the directory format supports the notion of an
optional number of "additional information words" where the first one is
defined as the date word.  Most people just leave the defaults set, so
the anomolous date is all they use, etc.  However, the OS/8 directory
structure is problematic, and if there are many small files, the directory
can run out of entry space long before the device runs out of physical space!
In that kind of situation, people jettison the first AIW, and then there is
no date on the file at all.

If the device can tolerate further intrusion into the directory space, then
it's possible to store an additional AIW to store the extension to the date.
There is no current support for this, but it could be easily added.  While
at it, the additional word can store additional year group bits to extend
the usefulness of the overall date reckoning.  Upgrading the rest of OS/8
to implement the year extensions is another matter entirely!  Additional
bits must be found to support the additional year offsets, etc.

An alternative would be to declare an imputed group offset.  All this means
is that you can't fake the past as easy!  The system could be defined in
terms of a patch made to some centralized routine.  (Note: the image of OS/8
PIP is currently used as the arbiter of device physical size!)  Thus, the
total date is the 32 year span of what's in memory plus eight times an
imputed value taken from the centralized routine, etc. which is used to
set the date, etc.

If all of this is done, then only files with a single AIW are anomolous,
and files with no AIW have no date, but then all the rest of the files will
have unique dates as far forward as any of us could want!

(I suspect this is part of what's going into OS/8 V5 :-).)

cjl

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From: [email-masked]
Date: 20 Sep 93 10:02:16 MDT

In article <[email-masked]>, [email-masked] (Charles Lasner) writes:
>  However, the OS/8 directory

OS/8 is certainly not the only operating system with this problem. CP/M and
RT-11 spring to mind. I don't know enough about the Un*x file structures to
be sure, but I suspect that even on Un*x you could run out of inodes before
you've filled up the disk.

Roger Ivie
[email-masked]

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From: [email-masked] (Jeff Makey)
Date: 20 Sep 93 18:19:39 PDT

In article <[email-masked]> [email-masked] writes:
>but I suspect that even on Un*x you could run out of inodes before

You could, but you don't have to.  With BSD-derived versions of UNIX
the ratio of disk space to inodes is a configurable parameter set when
you do a newfs(8) command.

                            :: Jeff Makey

Department of Tautological Pleonasms and Superfluous Redundancies Department
    Domain: [email-masked]    UUCP: nosc!crash!jeff