Port-vax archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: installboot is broken

On 2013-03-24 22:20, Anders Magnusson wrote:
On 03/24/2013 10:07 PM, Mark Pizzolato - Info Comm wrote:
On Sunday, March 24, 2013 at 1:51 PM, Anders Magnusson wrote:
On 03/24/2013 08:08 PM, Mark Pizzolato - Info Comm wrote:
This issue CAN and SHOULD be fixed.  However, there is a fundamental
chicken and egg problem here in that every available NetBSD vax ISO
going back to the earliest available (NetBSD 1.6.2) are all missing
this boot
block on that media.  Clearly no one has attempted to install any
version of
NetBSD on a legacy VAX (one which boots without the aid of a ROM based
I have done that on all of them; since I actually wrote the code :-)
Something has broken since then or you really never installed from a
CD.  These systems generally didn't have CD drives...
True.  I do not ever think I have installed from CD.

I actually have done this, but with a slight twist. dd the CD onto any RA disk, and then you're set to go. (I also have the VMS 7.3 CD on an RA disk, from which I then did my VMS installation on the 8650 from.)

This issue came to light due to efforts to use NetBSD with the
latest simh's
new VAX simulators (VAX 11/730, VAX 11/750 and VAX 8600/8650).  All of
these systems use VMB to initiate the bootstrap process and since
the disk
being booted doesn't contain a Digitial ODS2 disk structure, they
boot using
they achieve a boot using the bootstrap code provide in sector 0 of the
device being booted.  The systems with ROM based VMB have built in code
in the ROM VMB to use the pointers describing the bootstrap location in
sector 0 to directly load the rest of the bootstrap (usually from
sectors 1 thru
13) and dispatch to that.
You are not supposed to use VMB on those big machines.  You should load
boot directly from the console media.
This is how all BSDs always have worked.
I guess that might be possible (even on a VAX 11/750, you could always
boot thru the console TU58).  Given hard booting a dedicated loader
program the details of the boot block won't matter.  However, you'd
still have to make the TU58 media bootable.  The 750 Boot procedure
(for any device) loads sector 0 and starts execution at offset 2 of
the 512 bytes loaded.   There current isn't any code in sector 0.
This seems to be the installboot bug, yes.  But in some way it must get
the boot code installed sometimes; I installed NetBSD 6 on a fresh
4000/600 just a few months ago.  It had VMS on its disks before.  (Or
maybe I did some creative to get it work but do not remember it :-)

Ha! Yes! That is the point.
The MicroVAX, as well as probably all "new" VAXen use the boot block in a different way. They just read the boot block in to get a couple of magic values, and then start execution from data read in from block 1. The ROM-based VMB have been working right all the time.
It is just the console based VMB.EXE which this does not work on.

Many systems I came into contact with from the early 80's onward
(mostly 750's then) booted BSD OSes directly from disk, No console
media in the picture.    Likewise, as Johnny mentioned, Ultrix has
always booted directly from the target media using a 'Boot Block' boot.
Hm, this is old time, but IIRC the problem was not the booting itself,
it was that my 750 did not have ROM for the RA drives.

That would be another, but maybe even more interesting problem. :-)

Also, there were some trickiness with the microcode patching which
needed to be done, it was not trivial to get it right.

We still have the microcode patch distributed with NetBSD. As far as I know, it originated in Ultrix.


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

Home | Main Index | Thread Index | Old Index