BSD vs. System V, one last thing...

[Guy Harris]

> I have always been hanging out on BSD systems, so I have little or no
> expereince on the deadly SV.  And all of it as a casual user, no
> compilations, etc.  I just found out (I know you people are going to say,
> "God you're stupid!") that SV has no virtual memory built in,

This is incorrect.  If you heard this from somebody else, don't take their word
for much else about UNIX, because their information appears to be extremely
out-of-date at best, and simply wrong at worst.

The VAX System V Release 2 version *does* support demand-paged virtual memory,
as do the later 3B2 flavors of S5R2.  S5R3 also has it.

> this makes absolutely no sense to me since unix had it all the way up to V7
> as I remember,

No version of UNIX publicly released by AT&T before the VAX System V Release 2
version had demand-paged virtual memory.  This includes V7 for the PDP-11, and
the 32V version for the VAX (basically close to V7).

Berkeley added it to the 32V version of VAX UNIX independently of AT&T.

Versions of UNIX running on PDP-11 hardware with memory management had "virtual
memory" in the sense that they had memory mapping (there have been long debates
on USENET about what "virtual memory" means in the past; let's not start
another one - I simply note here that some people would not consider the PDP-11
UNIX versions from AT&T to have had virtual memory); all the S5 releases from
AT&T have had "virtual memory" in that sense.

> and they scrapped vm for SV.

As you can see, they did no such thing.