UNIX History

[gwyn%brl-vld at BRL-VLD.ARPA]

From:      Doug Gwyn (VLD/VMB) <gwyn%brl-vld at BRL-VLD.ARPA>

Guy Harris has given much more accurate UNIX history notes than most
of what has filtered into the ARPAnet on this topic.  I would like to
add a couple of comments:

It was fairly easy to take the 6th Edition UNIX 11/45 floating-point
processor (FP11) support and add it into the 11/40 version for a
PDP-11/34.  One subtle problem with using the 11/40 kernel on an 11/34
is that the faulted-instruction restart code was not entirely correct
for the 11/34, although later the 11/23 was again 11/40-compatible in
this regard.  The 6th Edition UNIX floating-point support also had
some bugs that needed to be fixed if one was going to make heavy use
of floating-point on an 11/34 or 11/23, as we did at Geotronics Corp.

The most important Columbus product to appear in USG UNIX would
probably be the augmented "make", which is much nicer than the
7th Edition UNIX version, although still not perfect.

All it takes to make UNIX quite usable for real-time data acquisition
is:
	(1) plock(2) or equivalent to ensure that user-mode code is
	    memory-resident when needed.
	(2) strict priority scheduling, which can be as simple as
	    adding a privileged "real-time process queue" to the
	    existing scheduler.
	(3) data acquisition device driver and user-mode dual-buffered
	    program that cooperate nicely.
One of the past USENIX tapes contained Geotronics contributions for
items (1) and (2) for 6th Edition UNIX.  John Quarterman, now with the
University of Texas Dept. of CS, did a really nice job of making (3)
work for the proprietary 11/23-based system used in the field by
Geotronics Corp.