Hello everyone, I've found myself in the exceptionally fortunate circumstance of securing ownership of a MAC-TUTOR BELLMAC-8 SBC unit. It is still in shipment so I can't assess its operation yet, but I was wondering if anyone is aware of any surviving assemblers, linkers, etc. for this architecture? If not, I'm prepared to roll my own based on available documentation, but figured I'd ask to see if there's anything I can start with. From what I can tell, the main development environment was PWB, specifically the Bell System internal varieties, with the BTL edition of Release 5.0 literature describing things like m8as(1), m8cc(1), etc. as Division 452 Computer Center standard commands.
There is a bit of information here as well: http://ferretronix.com/march/sbc/mactutor/
Thanks for any tips! Regardless of how much I can manage to do with it, I'll be sure to get some good pictures and take some notes on what I am able to figure out with the thing. I presume the Gunkies wiki would be a good place to document that sort of thing?
- Matt G.
P.S. Pardon if this belongs on COFF, I figured since UNIX was the canonical development system and it is also a Bell Labs thing, I'd ask here first.
I noticed there are kexec talks this year at Linux Plumbers. Kexec, kernel
boots kernel, has had a 25 year gestation in Linux, but it looks like it's
finally coming together, driven by need.
Thereby hangs a tale.
in 1977, I was working at udel with Ed Szurkowski, the first sysadmin of
the Unix systems we got in 1976 (first machine was an 11/70). Ed was a
gifted engineer and did all kinds of neat work on v6. He later went to the
Labs once he got his PhD and I lost track of him.
Ed got tired of watching the bootstrap slowness, and wrote a system call
that did the following:
1. load kernel in memory from system call argument
2. put special signature in low memory telling bootstrap "look in memory"
3. reboot via reset.
Now, this works, because back then, ROM boot code did not zero memory.
Memory was unchanged across reset. So the bootstrap could find the magic
bits and start the kernel.
I've lost the code, I carried the listings for decades but finally dumped
them. A shame.
But I'm wondering: is Ed's work in 1977 the first "kernel boots kernel" or
was there something before?
> The array size} limit that I found through trial and error is (2^15)-1.
> Declaring an array that is [larger] results in an error of "Constant
required",
On its face, it states that anything bigger cannot be an integer constant,
which is reasonable because that's the largest (signed) integer value. Does
that version of C support unsigned constants?
Doug
It's a bit off-topic but Warren OK'd it: I'm trying to tidy the absolute
dragon's hoard I call an office, so I'm looking to give away some books
I haven't touched in years. These are free for the taking for anybody
who wants to drive to SF and get them. I'd really prefer for somebody to
take them all at once, of course.
- DEC PDP11/70 Processor Handbook
- DEC VAX11 Architecture Handbook
- DEC PDP11 Peripherals and Interfacing Handbook
- DEC Introduction to Programming (PDP-8)
- Programming Languages: History and Fundamentals (Sammet)
- Computer Networks, 1st ed (Tanenbaum)
- Modern Operating Systems, 2nd ed (Tanenbaum)
- Operating Systems Design and Implementation, 1st ed (Tanenbaum)
- Advanced Programming in the UNIX Environment (Stevens)
- Computer Architecture and Organization, 2nd ed (Hayes)
- Compilers: Principles, Techniques, and Tools (Aho, Sethi, Ullman)
- The Undocumented PC, 2nd ed (van Gilluwe)
- Cybernetics (Wiener)
If you want these, please email me *off-list* to set it up.
John
> From: Ron Minnich
> Ed got tired of watching the bootstrap slowness
This may be a dumb question (in which case, my apologies), but which part of
booting a PDP-11 UNIX was slow? And thus, which parts did he bypass in a
'quick reboot'? (I'm having a bit of a hard time working it out.) I can think
of the following stages as potentially being 'slow':
1 - reading in the kernel image from disk
2 - sizing/clearing main memory
3 - loading running /etc/init
3A - creating all the 'loqin's
3B - starting all the daemons/etc with /etc/rc
(There's obviously a conflict between 2 and 3*; one can't avoid 3* if one
does 2.)
Which ones did he want to avoid?
Avoiding 3* puts some limitations on the system, obviously, because it means
one has to keep running processes around; the process table has to have the
same format (and be in the same location - or it has to be moved before the
new system is started). (Technically, I guess one would have to save the
inode and file tables, too; there isn't enough saved data in the kernel to
re-open files, plus there are file read/write ocation pointers, etc.)
One could sort of do 2 also, if one were prepared to 1) swap all processes
out to secondary storage before 'rebooting', and ii) saving the process table.
> But I'm wondering: is Ed's work in 1977 the first "kernel boots kernel"
> or was there something before?
Are you talking about for UNIX, or across all operating systems? I don't have
that broad a memory any more, to know - did TWENEX have something like that?
Noel
Apropos of the virtue of negative subscripts.
> by pointing into the middle of another data structure you've created a
data aliasing situation
Not if all references are relative to the offset pointer. The following
example is silly, but I recently used exactly this trick to simplify
calculations on a first-quadrant (x,y) grid by supplying "out-of-bounds"
zeroes at (x,-2), (x,-1) and (-1,y). It was much cleaner to access the
zeroes like ordinary elements than to provide special code to handle the
boundary conditions.
/* Fill an N-element array with Fibonacci numbers, f(i), where 0<=i<N.
The recursion accesses a zero "out of bounds" at i=-1 */
const int N = 100;
int base[N+1];
#define fib(i) base[(i)+1]
void fill() {
int i;
fib(0) = 1;
for(i=1; i<N; i++)
fib(i) = fib(i-2) + fib(i-1);
}
Doug
Hello all,
I know that this isn't strictly a "UNIX history" question, but as I am
working with historic UNIX and this list contains a great number of people
who were instrumental in its development, I figured it would be appropriate
to ask here. If there's a better place for these sorts of questions,
please let me know.
I'm trying to figure out how the array size limits are set in the 2.11BSD
pcc compiler. I've looked through quite a bit of documentation but I don't
see anything that describes this. In theory on a 16 bit system I would
think that the maximum array size would be 64K, but the actual limit that I
found through trial and error is (2^15)-1.
Declaring an array that is too large results in an error of "Constant
required", which is being produced by c01.c in conexp().
https://www.tuhs.org/cgi-bin/utree.pl?file=2.11BSD/src/lib/ccom/c01.c
I did quite a bit of searching through the source but I was not able to
determine where this limit is being set. This is where my usual tools fall
apart. Normally since I have the source I would compile the program I want
with debugging turned on, and then do a backtrace so that I could see how
we got to conexp(). But as far as I can tell I can't get a backtrace,
since there is no option for debugging information in pcc; adb can only
tell me where a process stopped.
I would appreciate any enlightenment or pointers to other documentation.
Thanks in advance!
-Henry
Lyndon Nerenberg (VE7TFX/VE6BBM):
Oh come on Rob, you should know that for anyone over the age of 50,
the moment you see 'dd' your brain automatically switches to JCL
mode.
===
Rob doubtless got IBM out of his system back in the
late 1970s, when I think he was one of the authors
of a shell that brought the TSO experience to Unix.
Norman Wilson
Toronto ON
