[TUHS] Some resources for V6/PDP/SIMH newbs like me

Will Senn will.senn at gmail.com
Tue Nov 21 05:20:06 AEST 2017


While it's fresh, I thought I'd share some resources I've found helpful 
in learning about the venerable v6 as a relative newb...

Learning Unix V6 in the modern era is an interesting and enormously 
educational experience. In the process of using it I have had to learn 
how to host it in a simulator (SimH in my case, but there are others), 
install it, communicate with it, configure it, build special files for 
it, attach devices to it, communicate with the devices attached to it 
and to SimH, build a kernel, install the kernel, boot the kernel, work 
with a variety of media intended to work with it, extend it, and so on. 
In addition, I have had to learn a bit about the PDP-11 (as arguably the 
most convenient architecture for learning about V6), about its 
architecture, its instruction set, its devices, its memory structure, 
and so on.

None of this exploration would have been possible without the excellent 
work of Bob Supnik, Mark Pizzolato, and co. on the SimH pdp-11 
simulator, the Simh mailing list, Warren Toomey and TUHS for making the 
bits available, the TUHS mailing list, PUPS, Bitsavers, and a slew of 
readily available documentation and texts including these notables:

Setting Up Unix 6th Edition from the V6 Programmer's Manual
The Unix V6 Programmer's Manual in its entirety
The SimH and SimH PDP-11 Manuals
A large number of blogs with SimH specific V6 installation logs
The V6 Source Code and man pages (don't forget to install man - the 1bsd 
version works, and is superior)!
The DEC PDP-11/05-10-35-40 1973 Handbook (the 11/40 handbook is not as 
detailed with respect to memory management)
Lions's Commentary on the Sixth Edition source code

Now that I'm over the beginner's hump, so to speak, I'm exploring things 
differently and I thought I'd share some resources that I am currently 
finding useful and interesting in my explorations...

To bone up on assembly language, Lions's commentary is exceptionally 
helpful in explaining assembly as it is implemented in V6. The manual 
itself is really thin, and the source is a bit cryptic, for the 
newcomer. Lions explains the idioms used in the main source of V6. 
However, without a background in assembly language, Lions is pretty 
meaningless, so I went looking for something that was PDP specific that 
would bridge the gap and help me understand Lions's words. I found a 
number of texts that were really good. Most require a working RT11 
instance to actually try out the coding examples and do the exercises 
(SimH and Bitsavers to the rescue):

Arthur Gill - Machine and Assembly Language Programming of the Pdp-11
Charles A. Kapps and Robert L. Stafford - Assembly Language for the PDP-11
Glenn H. MacEwan - Introduction to Computer Systems: Using the PDP-11 
and Pascal
James F. Peters - The Digital Way: Macro-11 Assembler Programming (PDP-11)
Michael G. Schneider - The Principles of Computer Organization: With 
Assembly Language Programming for the PDP-11
PDP-11 Processor Handbook (pretty much any edition)
Thomas A. Frank - Introduction to the PDP-11 and its Assembly Language

All of these are useable with a running RT11 instance. But, I think the 
Peters and Frank books are the standouts. Peters because all of the 
exercises that I have tried (dozens) have worked as printed and Frank 
because he is rigorous in his treatment of the subject and builds up 
from digital logic all the way through program execution. Frank is an 
excellent complement to Lions work because he explains the details that 
Lions assumes.

To learn about digital logic, and a special thanks to Warren for his 
work on Crazy Small CPU, I have been introduced to logisim. It is a 
great playground for exploring digital logic. I had no idea that a 
sketchpad for digital logic simulation was available and accessible to 
the layperson. Logisim development stopped around 2014 and while there 
are a number of successors out there, I am using logisim-evolution:


The rabbit trails never seem to end... in order to learn how to use 
logisim, I went through the excellent tutorial and then went looking for 
a book of experiments in digital logic and found:

digital computer lab workbook from 1969

digital equipment corporation computer lab teacher's guide from 1968

These two are useable with very little modification as a source of 
digital logic exercises that work great with logisim and are related to 
the architectural lineage of the PDP-11.

These resources fit together nicely in my pursuit to better understand 
digital logic, the pdp-11, assembly language, and unix v6. In sum:

Source code for v6 for what really is supposed to happen in v6 operation
Lions for understanding Unix V6 sources and for unix assembly language 
PDP-11 Hanbook for quick reference on PDP-11 assembly language 
instruction set
Frank for assembly language details and for details on digital logic and 
its relationship to the PDP-11 architecture.
Logisim to test logic constructs
The digital lab workbook for practice with digital logic



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