[TUHS] Unix V6: Assembler Listings

Clem Cole clemc at ccc.com
Thu Jun 11 23:40:30 AEST 2020


On Thu, Jun 11, 2020 at 9:04 AM Paul Riley <pdr0663 at icloud.com> wrote:

> Clem,
> Thanks for that. So this would compile on modern machines to a cross
> compiler for V6 also running on a modern machine? I note you say macro11,
> so not a Unix “as” style syntax, is that right?
Yes - the AT&T syntax was much simpler/less sugar than the DEC assembler.
 But the differences are pretty easy to see.  IIRC that assembler generates
DEC style linker objects and there is a companion linker that can create
DEC binary objects (*i.e.* 'obj' files) as well as traditional UNIX a.out
format.   The entire tool suite was created originally to move code from
RT-11 to UNIX at Harvard and passed around the nascent USENIX community.
 IIRC that version was forked from a BSD 2.x/NetBSD source repository and
folks were adding some fields/features in the DEC obj format that RSX
supported that RT-11 did not.

Go hunting and see what you find.  My memory was that with the BSD 2.x
project, somebody added a DEC obj to UNIX binary (a.out) converter tool, so
that you could use ld(1) instead of using the DEC style linker that had
been included in the original.

It has been >>years<< since I was really familiar with any of this stuff.
 A question about it came up last fall/winter on the simh mailing listing,
which is where I found the the URL.

FWIW: I offered the modern port, assuming you might want to run some of it
as a cross-systems on a newer OS with a modern compiler.   But if you are
content running this on V6, then you might just want to go back to the
original.  As I said, my memory is that's in the original USENIX Harvard
tape.   All that should be Warner's archives if not other places on the

Just remember that a big problem with the original code is that it will be
written in pre-'White Book' C (that many of us learned years ago  - not
even ANSI of Second edition - this used Lesk's portable C library etc.).
 It sometimes looks a little strange to modern eyes.  Also if you go
looking,  IIRC, someone at Harvard ported the DEC Macro RT-11 library to
UNIX v6.  In the late 1970s, I remember tjk, Danny Klein, Tron McConnell
and I, plus some of the folks over in the bio-med group (whose names I have
forgotten) had to a number assembler codes that had been written for the
earlier RT-11 systems to Unix for one of the projects we had.  Some of it
got re-written in C, but I do remember we managed to use the Harvard
assembler somehow for parts of it.   If my memory is correct, early VMS and
messing with BLISS compatibility could have been mixed up in the project
somehow, but I've long forgotten the details of what we were doing at the

Have fun.
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