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From: spaf@stratus.UUCP (Gene Spafford)
Newsgroups: net.unix-wizards
Subject: What is this panic?
Message-ID: <110@stratus.UUCP>
Date: Wed, 28-Nov-84 13:57:40 EST
Article-I.D.: stratus.110
Posted: Wed Nov 28 13:57:40 1984
Date-Received: Fri, 30-Nov-84 04:38:10 EST
Distribution: net
Organization: The Clouds Project, School of ICS, Georgia Tech
Lines: 90

We've just recently brought up 4.2 BSD on 3 750 Vaxen.  Each Vax is
configured with 2 or 3Mbyte memory, Rev 7 CPU boards, DEUNA ethernet
drivers, a DZ-32 board, an RL02 disk, and a UDA50 disk controller
running 1, 2, or 3 RA81 disks.

All three machines keep dying with a (claimed) tbuf parity problem.
However, the value in the mcesr register indicates a bus error rather
than a tbuf error.  The PC of the last few faults was in some of the
UDA50 code (udrsp) or the hardclock routine, while others were in user
address space; this seems to rule out any likely direct correspondance
with any particular software module.

The problem appears whenever the machines are under load, but there is
no sure way to bring on the problem.  Rebuilding 2 or 3 copies of Unix
at the same time seems to bring it on regularly, but not all the time.
This problem is rather annoying, to say the least, and I've had little
success either tracking the problem down or getting much co-operation
out of some of our local DEC people ("If it isn't a problem that occurs
with DEC software, it isn't our problem.").

Has anybody out there seen this before?  Anybody have a fix or
suggestion where I go from here?  If so, please drop me some mail (I
don't always have time to read my news in this group).  I'm enclosing
some samples of the error summary printed on the console (and log)
whenever the problem occurs.

Thanks in advance.
--gene


machine check 2: cp tbuf par fault
	va 12f90 errpc 6dfc mdr aaaaaaaa smr b rdtimo 0 tbgpar 0 cacherr 5
	buserr 6 mcesr 9 pc 6df0 psl 3c00004 mcsr 80016
panic: mchk
trap type 2, code = 0, pc = 80000d76
panic: Reserved operand

machine check 2: cp tbuf par fault
	va 7fffeb38 errpc 157d mdr 2d smr b rdtimo 0 tbgpar 0 cacherr 5
	buserr 6 mcesr 9 pc 157b psl 3c00004 mcsr 80016
panic: mchk
trap type 2, code = 0, pc = 80000d76
panic: Reserved operand

machine check 2: cp tbuf par fault
	va 7fffec6c errpc c5f8 mdr 0 smr b rdtimo 0 tbgpar 0 cacherr 4
	buserr 6 mcesr 9 pc c5f8 psl 3c00000 mcsr 80016
panic: mchk
trap type 2, code = 0, pc = 80000d76
panic: Reserved operand

machine check 2: cp tbuf par fault
	va 8017dfd4 errpc 8001c1f8 mdr 7c smr 8 rdtimo 0 tbgpar 0 cacherr 5
	buserr 6 mcesr 9 pc 8001c1f3 psl c00000 mcsr 80016
panic: mchk
trap type 2, code = 0, pc = 80000d76
panic: Reserved operand

machine check 2: cp tbuf par fault
	va 800336c4 errpc 800271fc mdr 0 smr 8 rdtimo 0 tbgpar 0 cacherr 4
	buserr 6 mcesr 9 pc 800271f9 psl 4150004 mcsr 80016
panic: mchk
trap type 2, code = 0, pc = 80000d76
panic: Reserved operand

machine check 2: cp tbuf par fault
	va 800336c4 errpc 800271fc mdr 0 smr 8 rdtimo 0 tbgpar 0 cacherr 5
	buserr 6 mcesr 8 pc 800271f9 psl 4150000 mcsr 80016
panic: mchk
trap type 2, code = 0, pc = 80000d76
panic: Reserved operand

machine check 2: cp tbuf par fault
	va 800336c4 errpc 800271fc mdr 0 smr 8 rdtimo 0 tbgpar 0 cacherr 4
	buserr 6 mcesr 8 pc 800271f9 psl 4150000 mcsr 80016
panic: mchk
trap type 2, code = 0, pc = 80000d76
panic: Reserved operand

machine check 2: cp tbuf par fault
	va 7ffff1a4 errpc 8000b188 mdr 7ffff184 smr 8 rdtimo 0 tbgpar 0 cacherr 5
	buserr 6 mcesr 9 pc 8000b186 psl c00000 mcsr 80016
panic: mchk
trap type 2, code = 0, pc = 80000d76
panic: Reserved operand
-- 
Off the Wall of Gene Spafford
The Clouds Project, School of ICS, Georgia Tech, Atlanta GA 30332
CSNet:	Spaf @ GATech		ARPA:	Spaf%GATech.CSNet @ CSNet-Relay.ARPA
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From: irwin@uiucdcs.UUCP
Newsgroups: net.unix-wizards
Subject: Re: What is this panic?
Message-ID: <13700083@uiucdcs.UUCP>
Date: Fri, 30-Nov-84 16:49:00 EST
Article-I.D.: uiucdcs.13700083
Posted: Fri Nov 30 16:49:00 1984
Date-Received: Sun, 2-Dec-84 03:35:29 EST
References: <110@stratus.UUCP>
Lines: 14
Nf-ID: #R:stratus:-11000:uiucdcs:13700083:000:624
Nf-From: uiucdcs!irwin    Nov 30 15:49:00 1984


We have 7 Vax-750s. Ours are all at Rev 3 CPU. We have the exact panic
you have described on 3 of the 7 quite frequently. We have a Ramtek
on one that can cause a crash from time to time, but this is a different
bug. We know that if the CPU were at Rev 7 the Ramtek bug would go away.

We have wondered if our machines were at Rev 7, if the panic bug would
disappear. Yours is at Rev 7 and do it, so that answers the question.
What causes it, still do not know.

Our disks are on CMI controllers, some CDC 300MB, some Eagles, some CDC 80MB.
Two of the 7 have hdwr floating point, no two of the seven are configured
alike.

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From: irwin@uiucdcs.UUCP
Newsgroups: net.unix-wizards
Subject: Re: What is this panic?
Message-ID: <13700084@uiucdcs.UUCP>
Date: Tue, 4-Dec-84 10:06:00 EST
Article-I.D.: uiucdcs.13700084
Posted: Tue Dec  4 10:06:00 1984
Date-Received: Thu, 6-Dec-84 03:48:38 EST
References: <110@stratus.UUCP>
Lines: 26
Nf-ID: #R:stratus:-11000:uiucdcs:13700084:000:1539
Nf-From: uiucdcs!irwin    Dec  4 09:06:00 1984

What is this panic? I had the opportunity to set down and have a talk
with the manager of our local branch of DEC.

To quote, "The 750s have a problem with translation buffer parity errors
when running 4.2BSD, if the Rev 7 has not been installed. (tbuf panics)
These errors go away if the machine is brought to Rev 7. In addition to
this, 4.2BSD also has problems with cache memory parity errors, which
also cause panic type crashes. These will be fixed with Rev 8, which will
be available in the spring of '85. There are fixes in our software, both
VMS and our version of UNIX, which gets around the bug, but not in 4.2."

I let him read the base note, to which this response is made, and pointed
out that the author stated that their machine was Rev 7 and was having
tbuf panics. He said that is the first case he knows of where those type
of crashes were a problem on a Rev 7 machine, running 4.2 and that there
well may be a hardware problem and may need a board replaced.

As to the memory time outs in the response before mine, it well may be
that the bug is a bad memory board. If there is a steady stream of errors,
the controller may be busy correcting errors, while at the same time getting
more errors, which hangs the controller so long that it does not respond
in time and a time out is declared. If 4.2 is being run on this machine,
it usually reports memory errors, and a look in /usr/adm/messages will
verify if there is a bad board. If there are, if the board can be removed,
it may be that the time out bug will go away.