[Simh] Getting to the 780 console prompt

[Stephen Hoffman]

Robert Jarrett wrote

On Thu, 23 Apr 2009 18:26:54 +0100, Robert Jarratt wrote:

> OK, I understand that the diagnostics would not work, but I have  
> been trying
> to modify R5 using the SIMH DEPOSIT command before booting the 780  
> to see if
> I can get it do a conversational boot (R5=1) or anything else. It  
> does not
> seem to react to any R5 values, except 0x10 which seems to cause  
> some sort
> of hang. Should I expect it to do a conversational boot if I try  
> this (DEP
> R5 1)?

Can we start with what problem you're trying to solve here, and not  
with a proposed solution and the ensuing discussion?   And I don't  
mean the literal "boot the diagnostic supervisor" by this.

Some background and some pointers...

With a typical VAX, depositing 10 into register R5 prior to loading  
and launching VMB causes the VMB image (whether embedded in the  
console ROM, or loaded from the console media, or loaded from the  
system disk, or files that are referenced by the simh FLOAD from the  
RX01 console floppy image) to go look in the file  
SYSMAINT]DIAGBOOT.EXE as the secondary bootstrap, which launches the  
Diagnostic Supervisor (DS).  Some boxes can network boot DS, and many  
can boot DS from tape media.

The available VAX boot flags are (also) available via the site http://www.hoffmanlabs.com/vmsfaq 
  (also at http://labs.hoffmanlabs.com/node/1) and that site has a  
"newer" edition of the OpenVMS FAQ than what's posted at HP, or you  
can snag the "newer" edition off of Freeware V8.0.  You can download a  
PDF or other formats from the HoffmanLabs web site, as well.

Most (recent) OpenVMS VAX releases have a tool known as EXCHANGE,  
which can access the RT console media.  That tool is underneath  
CONSCOPY.COM on various OpenVMS VAX versions, and how you managed the  
VAX RX01 media with OpenVMS.  IIRC, EXCHANGE arrived around V4.0 or  
so.  (Prior to that, the RSX tools and MCR tended to be used.  PIP?   
It's been a very long while since I tried RX01 console access from  
V3.x...)

The VAX-11/780 console worked from boot command files and not from  
anything resembling a console prompt; the LSI-11 was good for its time  
but is now very limited.  With the VAX-11/780, there was usually a  
DSBOO.CMD or some such set up on the console storage device for this;  
you'd usually end up editing DEFBOO.CMD to do what you need, and  
create SYFBOO.CMD or DSBOO.CMD or some such local name.   This  
involved using EXCHANGE or CONSCOPY, too.  With the simh emulation,  
the console is rather different than that of a "real" VAX-11/780 box.   
You've probably already found the documentation at http://simh.trailing-edge.com/pdf/vax780_doc.pdf 
  document, but that points to the use of the (far more recent)  
MicroVAX-style console with the simulator.  Which means BOOT dev / 
R5:10 is the usual command to (try to) get the DS going here on the  
VAX-11/780 emulation.

There's a copy of the VAX-11/780 diagnostic supervisor manual at MANX  
at http://vt100.net/mirror/hcps/ds780ug2.pdf for reference, though  
there needs to be some recognition of the presence of the emulation  
and not real hardware.  There are various other VAX diagnostic-related  
documents posted on MANX, too.

Finding out whether DS passes simh and simh hardware is certainly  
interesting, but few folks are looking to verify the simulator.  And  
those that are hopefully have access to the AXE (and MAX) VAX  
architecture verification tools; those are the old DEC tools for  
verifying a VAX processor and its instruction set.  AXE (and MAX)  
doesn't do all that much for verifying the I/O and the system  
environment.  (I don't know if Bob S. or Tim S. ever got his hands on  
these tools.)

Getting various versions of (as it was then known) VAX/VMS to boot on  
the VAX-11/780 also depends on the particular implementation of the  
simulator, too.  IIRC, you needed V3.0 to be able to boot with C- 
series MS780 memory, for instance.  There were various hardware and  
version inter-dependencies lurking back in that era; it was quite  
common to need a specific new VMS release for a specific hardware  
giblet.   For the 20th anniversary, Andy G. and I and other folks  
tried to scrounge up and put together a VAX-11/780 that could boot  
V1.0, but we couldn't get the right (working) pieces.  (And some folks  
chucked some what we had acquired, but that's another story.)

But (my) real question here is around what you're up to here; why  
you're looking to launch the DS.  Whether this is a hobbyist interest,  
or a production-level server migration question at its kernel.  The  
answer to this can take the discussion in a number of different  
directions.