31 Dec
2018
31 Dec
'18
12:51 p.m.
From: Will Senn
We are seriously considering upgrading our PDP 11/40
clone (SIMH), to a
PDP 11/45 (preferably another SIMH)
Heh! When I saw the subject line, I thought you wanted to upgrade a
_physical_ -11/40 to an -11/45. ('Step 1. Sell the -11/40. Step 2. Buy
an -11/45.' :-)
for our Unix v6 installation.
Why on earth would an organization have such a thing? :-)
Our CEO was traveling and met a techie in first class
(seriously,
first class?) who told him that we needed one.
Heh. If said techie knows about the two, he's probably pretty senior (i.e.
eligible for Social Security :-), and thus elegible for first class... :-)
It has fairly low utilization - a developer logs in
and writes code
every few days
Who the *&%^&*(%& is still writing code under V6?!
And how do you all get the bits in and out? (I run mine under Ersatz-11,
which has this nice device which allows it to read files off the host file
system; transfering stuff back and forth is a snap, I do all my editing with
Epsilon on my Windoze box, 'cause I'm too lazy to bring up the V6 Emacs I
have.)
1. Are there any v6 specific concerns about upgrading?
Not that I know of.
2. Why should we consider taking the leap to the
11/45? Everything
seems to work fine now.
You're asking _us_?
Some larger applications will only run on an split-I-D machine, is about the
only reason I can think of.
Oh, also, the floating point instructions on the /45 are the only kind
understood by V6; the C compiler doesn't emit the ones the /40 provides. Any
floating point code run on the /40, the instructions are simulated by a
trap handler (by way of the OS, which has to handle it and reflect it to
the user process). I.e. very slow.
3. If we jump in and do the upgrade, how can we
immediately recognize
what has changed in the environment? I.e what are some things that we
can now do that we couldn't do before?
See above.
4. If we just insert our current diskpacks into the
new system, will it
just boot and work? Or what do we need to before/after booting to
prepare/respond to the new system?
Any V6 disk pack can be read/mounted on any V6 machine. Any binaries (the OS,
or user commands) for the -11/40 will run on the -/45. (Which is why the V6
dist includes binaries for /40 versions of the OS only.)
To make use of the /45, you need a different copy of the OS binary, built from
a slightly different set of modules. (Replace m40.s with m45.s; and you will
need to re-asssemble l.s, prepending it with data.s.) Both variants can live
on the same pack, under different filenames; select the right one at boot
time.
5. Is 256K enough memory or what configuration do
y'all recommend?
256KB is all you can have. Neither SIMH nor Ersatz-11 support the Able
ENABLE:
http://gunkies.org/wiki/Able_ENABLE
which is what you need to have more than 256KB on a UNIBUS -11.
From: Clem Cole
You'll probably want to configure a kernel for
the 45 class machine.
Look at the differences in the *.s files in the kernel.
More importantly, look at the 'run' file in /usr/sys, which has commented
out lines to build the OS image for /45-/70 class machines.
But either way you should configure the system to use
the largest drive
v6 has.
This is actually of limited utility, since a V6 file system is restricted to
65K blocks _max_. So a disk with 350K blocks (like an RP06), you'll have to
split it into like 5 partitions to use it all.
From: Will Senn
Do you know of some commonly used at the time v6
programs that needed
that much space?
Heh. Spun up my v6, and did "file * | grep separate" in /bin and /usr/bin,
and then recalled that V6 was distributed in a form suitable for a /40. So,
null set.
Did the same thing on /bin from the MIT V6+ system, and got:
a68: separate I&D executable not stripped
a86: separate I&D executable not stripped
bteco: separate I&D executable not stripped
c86: separate I&D executable not stripped
e: separate I&D executable not stripped
emacs: separate I&D executable not stripped
lisp: separate I&D executable not stripped
mail: separate I&D executable not stripped
ndd: separate I&D executable not stripped
s: separate I&D executable not stripped
send: separate I&D executable not stripped
teco: separate I&D executable not stripped
No idea what the difference is between 'teco' and 'bteco', what
's/send' do,
etc.
Is there any material difference between doing it at
install time vs
having run on 11/40 for a while and moving the disk over to the 11/45
later?
No; like I said, you can have two different OS binaries on the disk, and
select which one you boot.
On a related note, how difficult is it to copy the
system from rk to
hp? I know I can rebuild, but I'm sure there's a quicker/easier method...
Build a system with both, and then copy the files? I'd use 'tar' (I have a
V6
tar, but it uses a modified OS with the smdate() call added back in) to do the
moving (which would retain the last-write dates); 'tp' or 'stp' would
also
work.
The hack _I_ used on simulated systems was to expand the file that held the
'disk pack', mount it as a different kind of pack (RL or RP), and then go in
and hand-patch the disk size in the root block with 'db', then 'icheck
-s' to
re-build the free list. Note: this won't give you more inodes, so you may run
out, but the usual inode allocation is pretty generous.
Noel
PS: Speaking of the last write dates, I have versions of mv/mvall, cp/cpall,
ln, chmod etc which retain them (using smdate()). If there's an actual
community of people using V6, I should upload all the stuff I have. Although
it might be good to establish some central location for exchange of V6 code.
However, I don't and won't (don't even ask) use GitHub or any similar
modern
thing.