Goodness! I joined this conference only to find out that there's nothing in it
and what's worse, I'm the FW. I guess that's only fair, since I requested a
conference of this nature. What I'm interested in (at least initially) is a
forum for exchanging information on hardware (and other interesting things). I
have been acquiring a lot of "obsolete" hardware from my place of employment
and there is usually not any documentation. Most of this junk I intercept on
its way to the dumpster (and a very high percentage of it still works). I think
that a lot more of it is salvageable but I can't tell for sure because I have
no idea what the switch settings should be on various boards. I have been able
to get my hands on a fair amount of documentation of one sort or another and
have had the opportunity to try a lot of things. I suspect that there are more
people out there that do the same. So here we go ...

60 responses total.

i use to work for such a co.  i would intercept hundreds of thousands
of dollars forth of "junk" on its way to the dumpster.  lot of it was
junk, but not all.  now i work for a much smaller concern which is not
yet making any money.  what goes out in the trash here is all junk.

Wait a year ...

I know what you mean, Fred. For years I made PDP-11s in their various forms
work for a number of clients. Now I find the things on the fast track to the
landfill. I find it VERY difficult to refuse to provide them a home in their
latter, obsolescent years. Like some people and stray cats. ;)

I have 4 PDP-11/40s available to a good home. Were running when taken out
of service.

What are they? ;)

A 16-bit minicomputer from the early to mid 70's.  A "medium" size PDP-11,
supports MMU but not split I/D.  The next generation was the PDP-11/34,
and the generation after that the PDP-11/23.  In the process it shrank
from a 6 foot tall rack stuffed with stuff, to a desk top machine.

So how big is this PDP-11/40, and what does it run?

   Ric, take my word for it, you don't want to use it as a computer.
A coffee table, yes, but not a compter.

It runs V6 Unix.  Maybe BSD 2.9.  It doesn't have split I&D, so the
kernel can only be 64K...You can't fit much Unix in 64K.

Maybe you can find a version of CP/M for it.

(for those of us who started computing after 1975, could you explain
what "I&D" is short for?)

Instruction & Data.  "Split I&D" means that "instruction" and "data"
space can be split between two logical memory segments, instead of being
combined into one, flat memory space.  Usually this is done on machines
that can only directly address a small amount of memory (on the PDP-11,
this "small amount" is 64K, since there are only 16 address lines) to
expand the maximum program size and still allow the kernel to relocate the
program in memory without an MMU.

As an example, the Intel 8086 chip has the concept of separate "code
segment" and "data segment" registers; when a program needs to address
a location in its data space, it refers to it as "ds:xxxx", which means
"give me whatever is xxxx bytes from the beginning of the memory segment
named by the DS register".  Similarly, programs can refer to instructions
as "cs:xxxx", which is the same thing, only relative to the segment named
by the CS register.  This allows the kernel to move the program's memory
location (say, to swap it out and then swap it in to a different location)
and allow the program to continue executing, simply by changing the value
of the CS and DS registers to reflect its new location.  This is different
from non-split I&D operation, where all memory locations are specified
relative to a single location; thus on a processor with maximum 64K
address space, a non-split program can only be 64K, but a split program
can be up to 128K (split between a 64K instruction segment and a 64K
data segment, of course).  This is almost as useful as having a bigger
address space; it falls down when you have a program that needs more
than 64K of instructions or data.

[Of course, this doesn't work so well on the 8086, since it has no concept
of a "supervisor mode" for the CPU, and thus a program can go ahead and
change CS and DS on its own to address different parts of memory; perhaps
memory that it shouldn't have access to.  This is why Unix running on the
8086 is very insecure; a malicious program can very easily modify its
process table entry in the kernel to, say, change its UID to 0.  Since
the 8086 has no memory protection, the program can do this without the
kernel noticing, or even caring.  More modern and better-designed chips
(chips that were, perhaps, designed with multitasking in mind) will not
allow a program to change or otherwise access memory it doesn't "own" --
my hypothetical program will dump core on any reasonable CPU running Unix.
(And this is why, BTW, it's impossible to impliment a secure Unix on
an 8086 or 8088.)]

The PDP-11 is a 16-bit machine -- that means the word size of the
machine is 16 bits -- pointers and everything.  That limits the size of
a program to 64K.  However, it turns out that it's pretty easy to divide
up your program into "code" and "data" pieces -- code is "executed", and
fetches generally go from the program counter, & nothing else does - so
it's nice if you can actually store your code somehow "separate" from
the data, so that it doesn't eat up any of the data space.  That's just
what split I/D is -- split instruction (code) and data space.  Means you
can have up to 64K of code, *AND* up to 64K of data.

No, you can't find CP/M for the PDP-11.  You can, however, run RT-11 on
it, which is kind of similar.  RT-11 is DEC's single user offering, and
the more advanced versions support foreground/background job processing.

You could also run RSTS/E on it - RSTS/E is kind of DEC's equivalent to
Unix for the PDP-11 series.  Basicaly, it's just a small timesharing
system - it does have the one nifty feature of being able to run
programs intended for other DEC pdp-11 Os's, such as RSX-11M, RT-11,
etc.  (RSX-11 is yet another possibility, kind of half-way between RT-11
and RSTS/E, and also an ancestor of VMS.  There's also something called
"DOS, and something called "IAS".

[Marc slipped in...]

        I just got a old computer an TSR-80.  Does anyone know what
type of software it uses?  I havent been able to open it up, 
dont have the right tools. ACK!  Well i am goint to get another
computer form my school, YES!  An espion and something else.
Well waiting for help, and where i could get the right tools.
Virl

re:#13
Unless it's a Model IV it'll only run warez specifically written for it, d
despite the fact that you MAY have a CP/M emulator for it (it's not compatible
with real CP/M), only the model IV's CP/M emulator was standard CP/M. If it's
a Model I pack it up and keep it somewhere it's almost a museeum piece. MIKE..

I use to have one of those back in the 70's!

Hello, everyone. I'm the new FW to hardware. Any junk collector could
have been, so it might as well be me. My intent is that this conf
run just as it has been, which, incidentally, is much like any other
junk box: we toss in stuff that used to work, and draw from it parts
and inspirations for new concoctions. Today is flea market day, so all
the boxes are out, and I invite you to do a good BROWSE through them,
and maybe stir them up a bit, for who knows what goodie might be down
at the bottom. Best of all, everything's FREE - but if you take out
a thingy, please put in another, so we can keep the boxes at least
up to the last generation.

You ever get the feeling that all the junk at the bottom of all
those "misc" boxes starts to breed after a while? I do.

Yea, but never into anything useful!

 ....... until 2 days after you toss it ......

Hmmmm.... I'm the sole fw here, currently, but someone added the quote
from -R2D2 - who with root is fooling around?

Probably whoever took the chips.

I'm new to this conference. I have a Z-183 Zenith laptop computer with
an 8088 processor. When I bought the computer several years ago there
was an option of a 1 Meg memory expansion. I didn't purchase this option
and when I inquired about it now was told that it is no longer available.
Does anyone out there know where I might obtain this option. The old part
number is ZA-180-47, the new part number is 971-0196 and the description 
is 1MB EMS RAM option. If you can help me with this, would you either
answer here or send me E mail at sail@cyberspace.org.

The Surplus Trading Corp., Benton Harbor MI (616-849-1800) claims
to have "replacement boards, drives, power supplies, batteries, etc."
for Zenith laptops and desktops. I haven't tried them. 

find Dan

How can I use Internet efficiently for job search?

Get the internet address for the person who's hiring for the Co. you
want to work for?

  Usenet offers some newsgroups related to job hunting.  Do you have access
to Usenet news?  It's not currently offered here on Grex.

        Okay folks, I've got a question for ya:  I was given a Viewpoint 
data terminal; I have no idea what it was being used for, or who owned it 
to begin with.  It has a 1983 date code.  Anyhow, there's a row of DIP 
switches next to the serial port.  I assume these set the baud rate, 
etc., but I have no documentation.  Can anybody help here?  The person who 
gave it to me mentioned something about jumpering two pins on the serial 
port to set certain variables, but couldn't remember what pins.

  How far have you gotten trying to do stuff with it?  If you want to
use it as a terminal to dial systems up, I'd stick on a modem, and see
what happens...do AT commands yield an "OK?"  Then try connecting to
places at the desired speeds, and flip DIP switches until it works.
(If you've already tried that, then sorry, dunno anything about that
terminal!)

Actually, a modern modem will adjust its baud rate to the terminal connected,
therefore bypassing the need to figure out the baud rate settings right
away.

        Yeah, I thought about that, I just haven't gotten a sex-change 
adapter for it yet.  I have a null-modem loopback, but it's the wrong 
sex, so I don't even know if the stupid thing works yet.  I guess I'll 
have to shell out the $5 for an adapter to find out.  As for what I'll 
use the beast for, I dunno yet.  Might be handy if my Mac dies, though.

There is a discussion in Item 27 of coop about a proposal to make Grex
conferences open to reading on the WEB without requiring readers to open
Grex accounts (called "anonymoous web reading of conferences"). An
argument in favor of doing this is that it could attract new participants
in conferencing after readers get a taste of what it is like. If you have
an opinion on this with regard to this conference, let us know: if you
have a opinion with regard to any other conference, you might start a
discussion of it there. In any case, you can read all sides of the issue
in coop item 27. 

Sounds good to me.

I believe that this conference should be visible to unregistered users.

Me too.

So do I.. but looks like this is never going to come up...

I have got a Brother Powernote PN-8500MDS)which only emulates TTY terminal
(what ever it means) and I find it dimpossible to send and read email. Could
someone suggest a way out? forget suggesting a nerw computer this is just 3
months old.

The only mail program I can think of, off hand, that will work with a simple
TTY is mailx.  It's not pretty, but it doesn't need a fancy display.

- Backtalk version 1.3.30 - Copyright 1996-2006, Jan Wolter and Steve Weiss