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From: grandi@noao.UUCP (Steve Grandi)
Newsgroups: net.bugs.4bsd
Subject: Re: mchk 2 --- tbuf error on 750 running 4.2 BSD
Message-ID: <427@carina.noao.UUCP>
Date: Tue, 30-Jul-85 12:56:05 EDT
Article-I.D.: carina.427
Posted: Tue Jul 30 12:56:05 1985
Date-Received: Thu, 1-Aug-85 21:21:40 EDT
References: <83@zeta.UUCP> <654@gatech.CSNET> <2496@sun.uucp>
Distribution: net
Organization: Natl. Optical Astronomy Observatories, Tucson, AZ USA
Lines: 41

> Okay, I will.  I already mailed John, but perhaps this could be rehashed
> one more time.  The problem does lie in the L0003 board, but the solution 
> is easy.  VMS has microcode to alleviate these parity problems, and 
> using the /boot program which reads microcode off the disk, the problem
> can be easily solved.  Mike Karels wrote up a patch and we have been running

Unfortunately, loading the proper microcode is not the complete solution.
Witness the following console output--

Jul  4 02:10
machine check 2: cp tbuf par fault
	va 802246f4 errpc 8001433b mdr 505 smr 8 rdtimo 0 tbgpar 3 cacherr 1
	buserr 8 mcesr c pc 80014336 psl c00000 mcsr 80318
panic: mchk
trap type 2, code = 0, pc = 80000fa2
panic: Reserved operand
trap type 2, code = 0, pc = 80000fa2
panic: Reserved operand
trap type 2, code = 0, pc = 80000fa2
panic: Reserved operand
trap type 2, code = 0, pc = 80000fa2
panic: Reserved operand
trap type 2, code = 0, pc = 80000fa2
panic: Reserved operand

4.2 BSD UNIX #5: Mon Jun 24 17:12:19 MST 1985
real mem  = 5238784
avail mem = 4198400
using 231 buffers containing 524288 bytes of memory
etc.

Maybe the combination of microcode rev. 98 (which we are already using) and 
the rev. 7 L003 board (which will be installed Someday, Real Soon Now)
will cure the problem and eliminate these irritating crashs.  But I doubt it.

Now the real question: Does anyone know why the system sometimes goes into
the mchk/Reserved operand panic loop shown above instead of trying its normal
recovery?  This happens on about half of our tbuf parity faults.
-- 
Steve Grandi, National Optical Astronomy Observatories, Tucson, AZ, 602-325-9228
{arizona,decvax,hao,ihnp4,seismo}!noao!grandi  noao!grandi@lbl-csam.ARPA