Re: [TUHS] Some notes on running UNIX v6 in 2015, using SimH and a healthy dose of documentation

Warren, Thanks for the comment. I appreciate your feedback and will make appropriate changes. Next? I have been reading Lyons and it has taken me some time to develop enough background knowledge to make sense of his notes. A surface read of the notes will give a novice reader some idea of the major architectural components of the system, but a deeper read will require the reader to have knowledge beyond what is required of most modern software developers (PDP-11 architecture, assembly language, and UNIX are prerequisite). It will also require access to a lab where the ideas covered can be experimented with. A modern reader might be intrigued from a historical perspective, but may not be compelled to go to the trouble of learning enough about the past to recreate it or even see the its relevance to the present or future. Access in 2015 to a working UNIX v6 environment on a PDP-11 ala 1975 is as unlikely as it sounds. However, using SimH to simulate a functional PDP-11, with peripherals, a UNIX v6 tape image from 1975, and the documentation from that period, which, thanks to TUHS is now accessible, it becomes possible to establish a laboratory from which to experiment. The resulting environment is not only historically interesting, but technically interesting, as well. Many of the interesting bits about our current systems, even seemingly unexplainable things like magic numbers, have their genesis and rational in this early system. The v6 kernel weighs in at around 10k lines of code with a limited set of peripherals and yet it packs in features that were either unavailable in larger more established systems or may have been present in some form, but were orders of magnitude more lines of code and attendant complexity. It was and remains an amazing operating system and worthy of contemporary study. So, I was thinking that next up, I would write up notes to help the modern reader engage with v6 more easily in order to follow works like Lyons. Right now, I am working on notes related to using the v6 assembly and c languages to produce working code. While this may seem trivial to folks who are expert, or who have worked in the actual environments, it is not really so trivial for me or for other folks brought up on more modern computing platforms and I would like to both understand the workflows and to document them for others. Regards, Will