[Simh] VMS 4.6 won't boot from a Massbus disk

[Bob Supnik]

Thanks, Mark. How did you happen to have a 4.6 image?

Not sure I want to slow down the RP everywhere else for this one case, 
but an STIME of 30 probably won't make a visible difference to anyone.

/Bob

On 1/27/2011 5:21 PM, Mark Pizzolato - Info Comm wrote:
> 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"<petermallan at googlemail.com>
>> To: "Bob Supnik"<bsupnik at comcast.net>, simh at trailing-edge.com
>> 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<  bsupnik at comcast.net>  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
>>
>>
>> _______________________________________________
>> Simh mailing list
>> Simh at trailing-edge.com
>> http://mailman.trailing-edge.com/mailman/listinfo/simh
>>
>> _______________________________________________
>> Simh mailing list
>> Simh at trailing-edge.com
>> http://mailman.trailing-edge.com/mailman/listinfo/simh
>