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Date:      Tue, 17 Feb 1998 08:07:42 -0800
From:      Cy Schubert - ITSD Open Systems Group <cschuber@uumail.gov.bc.ca>
To:        "Mike Nowlin" <mike@viewsnet.com>
Cc:        "Steve Grandi" <grandi@noao.edu>, "Mike D Tancsa" <mdtancsa@sentex.net>, freebsd-stable@FreeBSD.ORG
Subject:   Re: I need a strategy for making my STABLE installation stable 
Message-ID:  <199802171608.IAA12427@cwsys.cwsent.com>
In-Reply-To: Your message of "Tue, 17 Feb 1998 01:03:22 EST." <004901bd3b69$c13dce60$0f689926@twikki.argos.org> 

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> 
> >I have been running the Adaptec with "Ultra" speed enabled.  Probably worth
> a
> >try to to set 10 MBps instead of 20 (and then perhaps 8?) and see what
> happens.
> 
> 
> Not directly related, but I have had similar problems using Adaptec 1540B/C
> SCSI controllers  on certain 486 motherboards under both Linux and FreeBSD
> 2.1 & 2.2...  Basically, the SCSI bus would get stuck, while the rest of the
> system tried to continue running...  (Kinda hard without hard drives!)  I
> messed around with it more on the Linux machines, and was getting "SCSI
> command timeout" messages -- the kernel was still running, but the rest of
> the system was basically not doing much of anything else.  I noticed that
> adjusting the I/O speed of the controller would change the frequency of the
> lockups, but never got rid of the problem completely.  Depending on the
> motherboard, sometimes decreasing the speed would help, while other times
> increasing it would help, but it still happened like clockwork under heavy
> SCSI activity...  (Like "cat /dev/cd0a > /dev/null"...)
> 
> Finally, I just got sick of the problem, picked up a couple Pentium 200s,
> and the same SCSI controllers run great on the new motherboards...
> 
> Go figure...
> 
> --Mike
> mike@argos.org

I used to have this same problem with my 486DX33 and subsequently P120 
while using a Plextor 4-spin CDROM attached to an Adaptec 1540CF.  The 
problem was there in 2.0.5 and 2.1.0.  It went away in 2.1.5 but came 
back in 2.1.6 and still exists in 2.2.x (I'm currently running 
2.2.5+patches).

What eventually solved the problem was to set a jumper on the Plextor 
CDROM drive to force it to run in single spin mode only.  Every time I 
upgrade to a new release I remove the jumper to see whether the SCSI 
bus hang still exists.  To date only 2.1.5 was able to use the CDROM 
drive at 4-spin speed.

I've also noticed that I was able to more consistently reproduce the 
problem by running concurrent processes against the CDROM drive in 
4-spin mode.


Regards,                       Phone:  (250)387-8437
Cy Schubert                      Fax:  (250)387-5766
UNIX Support                   OV/VM:  BCSC02(CSCHUBER)
ITSD                          BITNET:  CSCHUBER@BCSC02.BITNET
Government of BC            Internet:  cschuber@uumail.gov.bc.ca
                                       Cy.Schubert@gems8.gov.bc.ca




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