Setting rp STIME to 26 is sufficient to allow VMS V4.6 to complete its
boot.
The standard VMS driver is running when the issue is observed (i.e. when
the boot doesn't complete with rp STIME< 26). The executing PC is at
80008B1F is:
$ anal/sys
VAX/VMS System analyzer
SDA> e/ins 80008b1f
EXE$NULLPROC: BRB EXE$NULLPROC
SDA>
Clearly the OS Idle loop in that version.
- Mark
On Wednesday, January 26, 2011 at 5:39 PM, Bob Supnik wrote:
The performance of your host processor is irrelevant. The simulator
times
everything in instructions. Interrupts occur the same number of
instructions
after IO is initiated or completed, regardless of host processor
speed.
Are you using a "stock" version of SimH binaries on Windows, or are
you
running on Linux from binaries that you compiled yourself? If Linux,
then
which distribution and version, and which C compiler, was used?
As was suggested by another writer, try increasing RP STIME and RTIME
from
10 to 1000, and see if that makes a difference.
Finally, you could still be in SYSBOOT. After you type CONTINUE,
SYSBOOT
does its real work, which is loading VMS itself, setting up the memory
environment and tables, and starting the operating system. When the
hang
occurs, please type ^E and dump the state of the processor:
^E
sim> EX CPU STATE
[long printout]
and mail that information to me.
I find it interesting that the RP has successfully booted everything
from V1 to
V7 EXCEPT for V4. I'd dearly like to see SYSBOOT and the RH/RP driver
for
V4...
/Bob
----- Original Message -----
From: "Peter Allan"<[email protected]>
To: "Bob Supnik"<[email protected]>, [email protected]
Sent: Wednesday, January 26, 2011 3:07:43 PM
Subject: Re: [Simh] VMS 4.6 won't boot from a Massbus disk
Thanks to everyone for their suggestions.
To answer Bob's questions:
1) I am using the vmb.exe image that comes with simh
2) The hang does not occur in SYSBOOT. I can get into SYSBOOT, look at
the
parameter values, change them and type CONTINUE. That is when the
system hangs. Yesterday I tried a minimal boot by going into SYSBOOT
and
typing
SET/STARTUP OPA0:, but that did not help.
4) I will try using the Massbus and RP debugging capability and see
what it
tells me.
I am running this on a recently purchased quad-core system that is
rather
fast. I have simh set up on a system that is much slower, so I will
give that a
try to see if there is a difference.
Cheers
Peter Allan
On 26 January 2011 12:44, Bob Supnik< [email protected]> wrote:
I agree with Dave Hittner: the hang in booting VMS 4.6 from Massbus is
either a timing problem, or a bug in replicating some small detail of
the
Massbus controller.
Because booting from an RA81 waits in the same place (but eventually
succeeds), the "branch to self" loop where the simulator is waiting
appears
to be an idle loop, where VMS is waiting for some sort of event, like
a disk
interrupt. The disk interrupt may have occurred too soon and been lost
(a
problem which occurred in DEC PDP-11 operating systems and in BSD Unix
as
well). Or some detail that was unimportant in VMS 7.x mattered in VMS
4.x,
such as the handling of attention interrupts versus data transfer
interrupts.
For an example of the kinds of details that could go wrong, see
http://simh.trailing-edge.com/docs/massbusmystery.pdf , which
documents
an error in the 7.X driver sources for these disks.
What would be most useful would be a VMS 4.X source set, but up until
now,
no one in the community has found one. So here are some questions and
ideas for debugging this problem.
1. Are you using the VMB (primary boot) image that comes with the 4.X
series, or the default VMB image that comes with the simulator, which
is
from 7.2? While I don't know of any version skew issues, they could
certainly
exist. Does the same problem occur when booting with a 4.X VMB?
2. Does the hang occur in SYSBOOT (secondary boot), or in VMS proper?
VMS
runs at high virtual memory (8XXXXXXX), yet the branch to self is in
low
memory. If the hang is in SYSBOOT, the problem is likely to be easier
to solve,
as the environment is simpler. One thing to check: is memory
management
enabled?
3. Other users have reported success in getting early versions of VMS
to run.
I seem to recall that versions as far back as 1.5 have run
successfully. Can we
get a census of which versions have been successfully tested on the
780
booting from Massbus, and what version of VMB they use?
4. Both the Massbus controller (RH) and the device (RP) have debugging
capabilities. You can log every register read and write to see how far
the the
controller gets.
5. As a last resort, zip up your RP disk image and post it to an
uploading site,
like Megaupload, so that others in the community can try their hand at
the
problem. You'll need to include not just the disk image, but
configuration
data, as well as any auxiliary files (such as an earlier VMB, if you
use one).
/Bob Supnik
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