🚀 go-pugleaf

In article <90600001@datacube> berger@datacube.UUCP writes:
>
>Is there a configuration of MicroVax II that could easily boot either
>VMS or Ultrix/Unix?   Could we have two winchesters, one with Unix
>and one with VMS and at boot time select which one the system would boot
>on?

Yes.  We were doing this at one time during our transition to Ultrix.
It's fairly simple, all you need are two RD53's, one with 
Ultrix, the other with VMS.  When booting, you can specify which device 
you want to boot from.  For example, if you have Ultrix on drive 0 and
VMS on drive 1, you would boot Ultrix with

>>> B DUA0

or VMS with

>>> B DUA1

The tricky part is loading the OS on the disks because the DEC distribution
kits only allow you to build a bootable system on DUA0 (the lowest
numbered drive).  I got around that by physically swapping the two
disks.  It's easier to build VMS on disk 0 and then move it to disk 1
since VMS can autoconfigure itself to boot off any drive.  Ultrix needs
to have the kernel rebuilt and the /etc/fstab file changed if you move
it to a different drive after building the system.
I don't remember the exact way I did it, but we had a system with floppy
disks which made it a little more complicated, but once you've done
it, it's really simple to switch operating systems.  Unfortunately,
the disks are not accessible from the other OS.  Also, we did
not mount the VMS disk from Ultrix, and mounted the Ultrix disk as foreign
from VMS.

If you have never taken the cover off a MicroVAX, then I suggest you be
careful about moving the drives; although it's fairly straightforward, the
connectors are fragile and you have to be gentle with them.  They are a bit
tight and hard to get to, but if you slide the drives half way out, they
are more accessible.

	--Michael Bruck
	  Intel CAD, Santa Clara
	  ...{decwrl,amdcad,hplabs,oliveb}!intelca!mipos3!mike