Re: [TUHS] shared memory on Unix

I can't speak for the dates, but Ken did a hack to the OS to interface with his Chess machine. Recall that all the I/O on the PDP-11 was memory mapped, so as I recall he simply mapped a piece of kernel memory into user space. Was never privvy to the details. I do remember a conversation with Dennis about semaphores, though. He mentioned that no less than five groups inside of Bell Labs had hacked semaphores into the kernel. Each group did it differently. He thought they were all a bad idea -- his argument was, "what do you do if a process sets a semaphore and then dies? It's pretty clear that either releasing the semaphore or leaving it set would be catastrophic in some cases." (Of course there were other similar problems, such as a process closing its files and dying, and then the kernel discovering that the disc was full. Luckily, these days, the disc rarely gets full...) Also, a comment from my own experience with AT&T marketing. When I was responsible for the System V languages in Summit, I was told that a marketing group was staffed and that there was a person in charge of marketing the language products (at the time, C, Cfront (becoming C++), Fortran, Pascal, and Ada). I set up a monthly meeting with this person. The meetings went on for over a year, but *I never met with the same person twice!* It seemed that the only thing the marketing group knew how to do was reorganize the marketing group... At the time, a lot of people buying VAXes were running VMS because its FORTRAN was far better than UNIX F77 -- in particular, it had an optimizer. I started a project to build an optimizer for FORTRAN, and staffed it with several very good people. Every six weeks there would be an attempt to kill the project. Each time I'd repeat the argument for doing it, and it would be saved. We almost started to put these attempts to kill it on the calendar. At no time did I get any feedback, positive or negative, from AT&T marketing. When I left AT&T in early 1986, the optimizer, by now almost complete, was immediately killed again. I was later told by one of my former team members that it was revived several months later and finally made it out. And that the next year it was the best-selling add-on to System V. Steve ----- Original Message ----- From: arnold(a)skeeve.com To: <schily(a)schily.net>, <clemc(a)ccc.com> Cc: <tuhs(a)minnie.tuhs.org> Sent: Wed, 01 Feb 2017 11:33:05 -0700 Subject: Re: [TUHS] shared memory on Unix Clem Cole <clemc(a)ccc.com> wrote: this cover Sort of. I did some contract work for Southern Bell circa 1983. They were still part of the Bell System then. I worked on a PDP-11 running Unix 4.0. At the time, the policy was to release externally one version behind what was being run internally, so System III was released to the world while the Bell System was using Unix 4.0. I still have the manual; I'm pretty sure "PWB" and "Programmer's Workbench" are not on the cover, it was just called "UNIX". As UNIX 5.0 was approaching, someone decided that to be one release behind on the outside was dumb, thus the jump from System III to System V. The doc I have describes UNIX as an operating system for the PDP-11, the VAX 11/780 *and* the IBM S/370 series of systems and the source code directory had the machine dependent bits for the IBM. Too bad that stuff never made it out. It's too bad that all I have is just the paper, but that's all I could get. That was a fun job, I learned a lot. Over lunch every day I read a few more pages of the manual, basically reading it from cover to cover by the time I was done. What a great way to learn the system! Arnold