Re: Can you MOP boot an install kernel directly?

[Johnny Billquist <bqt%softjar.se@localhost>]

I'll just top-post to be lazy.

First of all, as you know, MOP is the "native" way to netboot DEC 
machines from back in the day. And MOP sortof fills the place of both 
DHCP and TFTP in one. But it's more targeted for the explicit need of 
netbooting and remote management. But in a sense, for VAXen, it would be 
great if we had the possibility of getting all the netbooting though MOP 
and not need DHCP and TFTP. Not sure if that is possible, though.

I guess MOP didn't really become that relevant with VAXen until the uVAX 
II (that one was able to netboot, right?). There were net-bootable 
PDP-11 systems as well, which also used MOP, and which were earlier. But 
pretty much all the handling of MOP on those machines were actually 
located in the ethernet controller itself. The CPU was pretty much just 
in a tight loop until the controller brought it out of there. But that 
was primarily for the PDP-11. On VAXen, MOP was implemented in the boot 
monitors. Not sure you can even use the MOP in the controller itself if 
you're on a VAX.
But so, for simh, the controllers do implement at least parts of the MOP 
on that side. For VAXen, with something like the 3900, the boot roms 
from the actual machine are included, if I remember right, and so MOP 
booting will definitely work there no matter what else simh might do.

  Johnny

On 2025-08-04 16:24, Anders Magnusson wrote:
> Den 2025-08-04 kl. 16:15, skrev Perry Metzger:
> > On 8/4/25 09:59, Anders Magnusson wrote:
> > > > Okay, so, I have a VAXstation 4000 VLC I'm setting up and I'd like 
> > > > to try to avoid needing a full NFS server, rarpd, and all the rest 
> > > > of that to boot it for installation (and as I am thinking of 
> > > > cleaning up some of the install tools I might be installing it 
> > > > repeatedly). One thing that struck me as a possibility was booting 
> > > > an INSTALL  kernel with an embedded ramdisk directly from MOP, 
> > > > another option struck me as fixing the network boot blocks so that 
> > > > they can use dhcp and tftp to download the kernel instead of 
> > > > requiring a full NFS setup. (Many ports allow this one way or 
> > > > another, either from the blocks themselves or from mechanisms like 
> > > > PXE.)
> > > Yes, sounds like something that would be smooth to have.
> > > - Adding support for tftp to boot is mostly trivial.
> >
> > Also dhcp. Which is also easy enough since libsa handles both. Then 
> > one can load an INSTALL kernel very easily over the network and 
> > install that way.
> DHCP is supported.  Needed to get the address of the nfs server :-)
>
> > > - Making the install kernel detect whether loaded via mop or is 
> > > probably not especially difficult either.
> > >
> > > Note that netbooting is something quite new in the vax world :-) It 
> > > was not until moj@stacken wrote mopd that it could be done at all, 
> > > before that I used boot on a local media (floppy) that loaded the 
> > > kernel from a SunOS4 machine.  Hence bootparams is also includedin 
> > > the boot program :-)
> >
> > Yah, it's certainly not something people would have wanted to do 45 
> > years ago but now it's pretty useful.
> :-)  I think MOP showed up some 5-10 years into the vax lifespan. No 
> need for it unless you are diskless, which came with MV2000 and friends 
> (some DEC gurus can probably give better explanations :-) )
>
>
> > Does SIMH support MOP btw?
> Good question.  A quick grep for MOP in pdp11_xq.c gives a lot of hits 
> though.
>
> -- R

--
Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt%softjar.se@localhost             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol