DMA (maybe) and tape drive problem (PANIC)

[Bill Vermillion]

In article <1990Aug20.052225.3371 at jersey> zaz at jersey.UUCP (Todd Koeckeritz) writes:
>I have run into a rather hard to solve problem and would appreciate
>any input all you netters might have.  I have a 386 (Mylex MX Revision
>1.01 25Mhz) motherboard, an Archive VP402 card controlling an Archive
>150M VP tape drive and an Adaptec ACB-2322B controlling a 300M disk
>all running under Xenix SysV 2.3.2.  The problem I am having is that I
>can write tapes fine (never had a problem here), but sometimes when I
>am reading the tapes I'll panic with a general protection fault or a
>non-recoverable kernel page fault.  This will happen whether I am just
>listing the files (as in tar tvf or cpio -iBtvc or even dd), dumping
>everything to the bitbucket (/dev/null) or actually attempting to put
>the files on disk.
 
[some details deleted - wjv]
 
>To me it has boiled down to three possibilities:
>1) A bug in the tape driver or Xenix, although I would expect to have
>   seen some other flames about this.
>2) A flakey tape controller card:  temperature appears to have some
>   effect.  It happens more "reliably" if my system cabinet is on than
>   when it is off.
>3) A problem with the motherboard (DMA Controllers or design)
 
>The only people I haven't talked to yet are Archive and the net.  SCO
>of course wouldn't talk to me (mail or voice) to confirm or deny any
>complicity, and Mylex disavowed that they had ever had a problem with
>their motherboards (I have heard they did from several sources, can
>anyone help to confirm or deny this ?).
>
>Has anyone ran into a similar problem ?  Or is their a known problem
>with any of the equipment I have mentioned ?  This is a last ditch
>effort to solve the problem before I must go down and away while I
>track Mylex and whoever else must get involved in solving the problem.

Well - I thought I must have been going crazy.  And from what you 
describe, your symptoms and my symptoms - the ONLY commond things
are SCO 2.3.2 and the '386 chip itself.

I have about 2 dozen systems I take care of.  One site has the
Maynard Maynstream drives and 12 interface cards.  The ONLY
problems I have had are with the machines running 2.3.2.  The 2.2.3
machines are fine.  The machines are IBM Model 80 MCA bus.     

I haven't had the tape read problem, as I haven't read that many.
But I get major problems with tape write.

It will either 1) stop and start counting memory as if from a cold
boot 2) just hang, 3) give me a non-recoverable page fault, or 4)
double-panic with a non-recoverable page fault.

I spent several hours on one of the machines and can make the crash
happen when I want it too.  All I have to do is write to the tape a
second time without rebooting.

>From a cold start it always works, and if the tape has been
written, and the machine not rebooted, trying to write the second
time will ALWAYS crash the machine.

I talked with Maynard (now an Archive company) and they deny any
problems.

I have another machine at another site that has an AMI motherboard,
8 megs of memory, DPT caching disc controller, a Maynstream 150 meg
tape (the others are 60's) and a totaly different set of serial
ports, Specialix and not Anvils.

The IBMs are 16MHz, the AMI is 20.  All the '286's with 2.2.3 run
flawlessly as did the '386s until the change to 2.3.2.  That
required new software drivers so I immediately blamed them.

I didn't know the latter machine was crashing as it was always
turned off at night.  The second time will usually lock the machine
up, though it has been spontaneously rebooted at times.

I had been leaning toward Maynard driver problems, but this leads
me to beleive there may be something in the SCO system causing it.

I have had the same results whether using tar or CTAR.  I tried
removing the tape drivers, and found the de-install script takes
some of the base system with it - and haven't had the time to do a
total re-install.  That bug in the script led me to think Maynard,
but your problems are SO similar I am now thinking OS.

So far that's two of us with strange problems.  Any one else with
strange lockups or reboots with 2.3.2 ?

bill

-- 
Bill Vermillion - UUCP: uunet!tarpit!bilver!bill
                      : bill at bilver.UUCP