On Tue, Jan 30, 2018 at 5:28 AM, Paul Ruizendaal <pnr@planet.nl> wrote:

For a while I had been wondering about the origins of a modification to the V6 kernel that places the kernel buffers in a separately mapped area, freeing up space for other things. It is used in some of the early networking code, i.e. both the UoI code and the V6 BBN code (as available on the TUHS Unix Tree).

I came across the following reference in https://www.osti.gov/scitech/servlets/purl/12130675:

“One widely distributed (though undocumented) solution to this hardware limit on the model 40 was a version of Unix by Robert Sidebotham, Faculty of Environmental Design, University of Calgary. His solution was to move the I/O buffers out of kernel space.”

This would explain the modifications being bracketed with "#ifdef UCBUFMOD”.

Some questions for the old hands:

- Was this patch indeed widely known / distributed?
​Hmm - a little like the halting problem I fear - how can you tell?

I can say we knew about them because Gosling brought them to CMU when he was a grad student; but by that time, we had started to switched to Unix/TS and Seventh edition that Ted had brought from BTL.   As I recall, it was more hacking/surgery then I personally wanted to do in the EE 11/34 based systems.  I don't think they got added to the SUS or IUS @ CS which were the other heavy 11/40 machines at the time.


- Widely distributed is not the same as widely used: was it?
​Not that I remember, but others of course may remember otherwise.

I think many of us knew that Calgary (and Toronto to an extent) was a hot bed of Unix hacking because of Gosling, but the places outside the US that were probably having the most effect on the community at the time were in OZ and the UK.  ​

​Remember Net.noise had not really started as UUCP was part Seventh Edition so the news systems are in the future.  Also the ArpaNet was limited in reach, and not that many UNIX sites were apart (it was mostly PDP-10s). Thus, unless someone came to a USENIX and talked about something, or a student somehow switch schools (like to be a grad student) folks did not know about the changes.​   For instance, I knew a little about what was going on at MIT and UMICH because of friends that left CMU and went to there or vise versa; and I would bring CMU things to UCB etc...