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

[will.senn@gmail.com (Will Senn)]

Noel,

Thank you for writing and responding to my writeup. I have replied 
inline, below:

On 12/3/15 9:21 AM, Noel Chiappa wrote:
>      > From: Will Senn <will.senn at gmail.com>
>
>      > I am studying Unix v6 using SimH and I am documenting the process
>
> I did a very similar exercise using the Ersatz11 simulator; I have a lot
> of stuff about the process here:
>
>    http://www.chiappa.net/~jnc/tech/V6Unix.html
>    
Thanks for reminding me about your work. I had scanned it briefly when I 
was first starting down this road, but wrote it off because I wasn't 
using the Ersatz11 simulator. With the background I have now, it should 
be translate into my current frame and be useful. I haven't tried 
tackling the time problem yet, but I will keep your document in mind 
along with Wolfgang's fixes for ctime:

     http://www.tuhs.org/Archive/PDP-11/Bug_Fixes/V6enb/

>
>      > the PDP architecture
>
> Technically, a PDP-11 ...
Oops. I will be more careful in how I refer to the PDP-11 from now on.
> The only differences I could discover between the two are that in the Wellsch
> versions i) a Western Electric rights notice (which prints on booting) has
> been added to ken/main.c, and the Unix bootable images; and ii) the RK pack
> images do have, as you noted, the bootstrap in block 0.
Thanks for this. I will update my note appropriately.
>      > Note: sh is critically important, don't muck it up :). The issue is
>      > that if you do, there really isn't an easy way to recover.
>
> One should _never_ install a new shell version as '/bin/sh' until it has been
> run and tested for a while (for the exact reason you mention). Happily, in
> Unix, as far as the OS is concerned, the command interpreter is just another
> program, so it's trivial to name a new binary of the shell 'nsh' or
> something, and run that for a while to make sure it's working OK, before
> installing it as '/bin/sh'.
This is a duh moment for me. I will change the note to reflect testing 
first, then copy over.
>
>      > a special file (whatever that is)
>
> Special files are UNIXisms for 'devices'. _All_ devices in Unix appear as
> 'special files' in the file system, usually (but not necessarily) in /dev -
> that location is a convention, not a requirment of the OS.
>
I have since learned a lot more about this and will update the note.

Regards,

Will