[Simh] Older Model VAX simulators, what can you do with them and how do they work?

[Mark Pizzolato]

On Sunday, October 9, 2016 at 4:58 PM, Johnny Billquist wrote:
> Oh, and another comment. More general, but anyway...
> 
> DEC did not really expect that tapes would be booted from on VAXen, so they
> did not provide any standard way to boot in this way. For the
> VAX-11/780 for example, if you got VMS on tape, you were expected to boot
> a small standalone version of BACKUP from floppies, and then do the restore
> of the tape from this environment.
> 
> The VAX-11/750 had a similar thing with the standalong backup environment
> on DECtape II.
> 
> However, MicroVAXen reintroduced booting from tape, as the TK50 became
> widespread, and the only removable storage on many of those machines. (I
> say reintroduced, since PDP-11s usually always included the ability to boot
> from tape.)
> 
> So the approach of not being able to boot from tape, that DEC decided on for
> the early VAXen, is a bit unfortunate, since it does make these kind of things
> extra hard, if you are not using VMS.
> 
> And this is why doc sets like MtXinu provided this information in their
> manuals, and why the instructions consist of writing actual code into memory
> to do the booting from tape.

As I vaguely recall, MtXinu didn't come into existence until after 4.x BSD Unix 
and when that happened, the VAX 11/750 certainly was a supported system.  

Meanwhile, Ray's original question was about installing 3BSD, which I think 
may have existed before the VAX 11/750 was available/supported...

Of course, my memory is vague at best.  In any case, the installation 
instructions for the original OS distribution would be the relevant place to look.

- Mark