11 Aug
2010
11 Aug
'10
4:23 a.m.
I managed to get 2.11 installed on SIMH, and hacked the de driver to work
(pretty much the same thing I did for 4.2 BSD on the 11/780) and now I've
gotten it networking.
I'll admit I'm not all that swift on the pdp-11, but I get the impression
that the maximum exe size is 128kb with 64kb of instructions, and 64kb of
data? Isn't there something that can be done with overlays or some other
linker thing to act like an 8086/80286 with the large memory model (ie
multiple segments...?)
I've been trying to build ircII-4.4 and I can't figure out how to link
something that big... I've tried the -Z and -O flags to ld to no avail.
Clearly I'm doing either something wrong, or impossible or stupid.
FWIW, here is the size of the same program on the VAX
myname# ls -l irc-4.4
-rwxr-xr-x 1 root 413696 Jun 8 08:46 irc-4.4*
myname# size irc-4.4
text data bss dec hex
293888 67584 20784 382256 5d530
I have a feeling that 300kb of text, along with 67kb of data is just too
much...?
Any pointers would be appreciated!
Jason
11 Aug
11 Aug
9:49 a.m.
Jason Stevens scripsit:
I'll admit I'm not all that swift on the
pdp-11, but I get the impression
that the maximum exe size is 128kb with 64kb of instructions, and 64kb of
data? Isn't there something that can be done with overlays or some other
linker thing to act like an 8086/80286 with the large memory model (ie
multiple segments...?)
The PDP-11 is inherently a 16-bit-pointer machine; it has no concept
of 32-bit pointers, so it is always either in the x86 small or the x86
tiny model. On DEC's operating systems, you could indeed set up overlays
that allowed code to be swapped in and out, either to disk or to unmapped
physical memory (much quicker!) However, AFAIK ld(1) never provided that
capability to userspace, although the technique is used inside the kernel.
In any case, such tricks don't help with data space, which is strictly
limited to 64K.
--
There is / One art John Cowan <cowan(a)ccil.org>
No more / No less http://www.ccil.org/~cowan
To do / All things
With art- / Lessness
10:45 a.m.
The PDP-11 is inherently a 16-bit-pointer machine; it has no concept
of 32-bit pointers, so it is always either in the x86 small or the x86
tiny model.
I guess it's logical that after the years, intel could at least make *some*
improvements....
On DEC's operating systems, you could indeed set
up overlays
that allowed code to be swapped in and out, either to disk or to unmapped
physical memory (much quicker!) However, AFAIK ld(1) never provided that
capability to userspace, although the technique is used inside the kernel.
In any case, such tricks don't help with data space, which is strictly
limited to 64K.
And that pretty much seals the deal. Oh well, it's amazing how big things
have grown over the years....!
--
There is / One art John Cowan <cowan(a)ccil.org>
No more / No less http://www.ccil.org/~cowan
To do / All things
With art- / Lessness
Thanks anyways!
Jason
1:27 p.m.
On Tue, 10 Aug 2010 18:23:00 -0400
Jason Stevens <neozeed(a)gmail.com> wrote:
I get the impression that the maximum exe size is
128kb with 64kb of
instructions, and 64kb of data?
Isn't there something that can be done with overlays
You are limited to 64 kB
of data. Code size can be larger then 64 kB
with the help of overlays. Have a look at how the kernel does this.
--
\end{Jochen}
\ref{http://www.unixag-kl.fh-kl.de/~jkunz/}
3 Sep
3 Sep
5:22 p.m.
Jason Stevens <neozeed(a)gmail.com> writes:
I'll admit I'm not all that swift on the
pdp-11, but I get the impression
that the maximum exe size is 128kb with 64kb of instructions, and 64kb of
data? Isn't there something that can be done with overlays or some other
linker thing to act like an 8086/80286 with the large memory model (ie
multiple segments...?)
There is. :)
I've been trying to build ircII-4.4 and I
can't figure out how to link
something that big... I've tried the -Z and -O flags to ld to no avail.
Clearly I'm doing either something wrong, or impossible or stupid.
IIRC, you want something along the lines of:
ld -i -o irc -Z a.o b.o -Z c.o d.o -Z e.o f.o -Y g.o h.o -lc
where -i says to use split I/D (64KB for each), each -Z introduces a set
of object modules to go into one overlay, and the -Y introduces the
object modules that are not to be overlaid. You'll want your main() to
be in the -Y group, ideally along with the most used parts of the code.
Each -Z group should ideally contain object modules that are all used at
the same time; the idea is to minimize the number of overlay swaps that
have to be done.
There are binaries in 2.11BSD that are built in this way. Look for the
-Z flag in the Makefiles.
Use size(1) on the a.out to see the sizes of the various overlays and
the main area: you'll get error messages from ld(1), and size(1) will
help you figure out how you need to move objects around to keep the main
area under 56KB, and each overlay under 8KB. (Actually, I seem to
recall that those limits can also be 48 and 16, or 40 and 24, and so
on. 'man ld' might be of help.)
FWIW, here is the size of the same program on the VAX
myname# ls -l irc-4.4
-rwxr-xr-x 1 root 413696 Jun 8 08:46 irc-4.4*
myname# size irc-4.4
text data bss dec hex
293888 67584 20784 382256 5d530
I have a feeling that 300kb of text, along with 67kb of data is just too
much...?
You might be able to squeeze it in. Your data space usage will be less
on a 16-bit system, and you may be able to reduce the sizes of arrays
and allocations here and there by accepting limitations in the resulting
program.
-tih
--
I don't believe that souls or bodies can be changed by incantation.
--Christopher Hitchens
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4 comments
4 participants
participants (4)
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Jason Stevens -
Jochen Kunz -
John Cowan -
Tom Ivar Helbekkmo