[TUHS] history of virtual address space

[Ron Natalie via TUHS]

Indeed, 4BSD had a zero located at location zero.

Amusingly the PDP-11 had code down there.     You knew you were 
dereferencing zero when “p&P6” showed up in your output.    This is what 
was left printable in the first few instructions of crt0.o (a setd 
instruction followed by others).


------ Original Message ------
>From "Rich Salz via TUHS" <tuhs at tuhs.org>
To "Warner Losh" <imp at bsdimp.com>
Cc "The Eunuchs Hysterical Society" <tuhs at tuhs.org>
Date 1/20/2026 11:49:25 AM
Subject [TUHS] Re: history of virtual address space

>On Mon, Jan 19, 2026 at 7:05 PM Warner Losh via TUHS <tuhs at tuhs.org> wrote:
>
>>  4.2BSD on the Vax dereferencing 0 would seg fault. I'm not sure when this
>>  started. I am sure that System V or 32V on the Vax dereferencing 0 gave
>>  0.
>
>
>Are you sure?  My memory is the opposite.  For example,
>https://www.tuhs.org/Usenet/comp.bugs.4bsd/1989-July/003016.html