[Simh] Ultrix 4.0 and DEQNA-LOCK

[Mark Pizzolato]

The pdp11_xq device simulates 3 boards:

1)      DEQNA

2)      DELQA

3)      DELQA-T

The DELQA documentation refers to specifically enabling DEQNA Lock mode which can be specified by switch and/or programmatically.

When implementing the simulator, beyond the fact that there is a DEQNA Lock mode, the document really doesn’t mention what is special/different about the behavior of the DELQA device when it is in DEQNA Lock mode.  VMS doesn’t handle the DEQNA and the DELQA differently beyond merely identifying one board from another.  VMS does detect the DELQA-T and it leverages the completely different/more efficient/less ambiguous programming model.

If someone can provide the various versions of the Ultrix drivers for this device and maybe explain how the different devices are treated differently by those drivers we can make the simulated devices more precisely match what the original hardware did.

From: Simh [mailto:simh-bounces at trailing-edge.com] On Behalf Of Cory Smelosky
Sent: Wednesday, August 31, 2016 7:52 AM
To: Johnny Billquist <bqt at softjar.se>
Cc: simh at trailing-edge.com
Subject: Re: [Simh] Ultrix 4.0 and DEQNA-LOCK

[inline]

Sent from my iPhone

On Aug 31, 2016, at 03:30, Johnny Billquist <bqt at softjar.se<mailto:bqt at softjar.se>> wrote:
Hi.

On 2016-08-31 04:43, Cory Smelosky wrote:

4.5 exhibits the same "now it's suddenly in DEQNA" mode behaviour.

Well, then I retract my guess. By 4.5 I would expect the code to handle a DELQA natively. Ragge also posted the source code for 4.5, which clearly states that it should handle the DELQA...

Yeah - I'm very confused by that!



(it also panic()s every first boot after first starting the emulator)

Huh. That really do sound like a bug. Since it don't happen on real hardware I would guess a simh issue. What kind of VAX are you emulating, by the way? The 3900?

Yup - 3900. It didn't occur to me until now it might not be coincidence it panics with a segfault right after probing the network card...I wasn't noticing any network issues until now though I guess.


   Johnny



On Tue, Aug 30, 2016, at 08:04, Clem Cole wrote:

On Tue, Aug 30, 2016 at 6:38 AM, Johnny Billquist <bqt at softjar.se<mailto:bqt at softjar.se>> wrote:
Not sure there are any bugs here. Ultrix might just change it to run in DEQNA mode. Maybe because it didnät have a driver for running it in DELQA mode in 4.0? Just guessing here, but it don't look to me as if there actually is a bug anywhere.

I've long since forgotten the details.    The 4.5 SPD says it should work (modulo firmware - which I suspect simh is assuming that).   Johnny is probably right.


Cory: Is there a reason you are running 4.0 not not something later than 4.4.   There a ton of bugs fixed in the 4.3/4.4 development.  The Vax has sort of been forgotten by the Ultrix/Tru64 teams in favor of the PMAX and the Alpha;  thus entropy had set in on the Vax code.   Even though 4.3 was not an officially bug release, it had more bug fixes in that any previous one, because a number of just got sick of dealing with it and there was a 3-4 week development hiatus where we just cleaned up things.  IIRC this was particularly true for the networking stack, because we were heaving pathworks development then and the Pathworks stack kept turning up small boundary conditions in the Unix side.

Anyway -- if you are going to run Ultrix, I highly recommend 4.5 - which was really the most stable of the all the Ultrix releases.  For instance, the SCSI stack is (finally) common with Tru64, as we back ported Fred's Alpha stack to the Vax and PMAX.   As a result it will cover a lot more devices.   I seem to remember we did some similar things in the Network code too, but again I've forgotten (I was worrying about TruClusters at that time but would occasionally consult to the Ultrix folks).
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