(LONG) problem with multiple scsi devices on ESIX machine

[Rick Kelly]

In article <1991Apr13.211855.4730 at unixland.uucp> bill at unixland.uucp (Bill Heiser) writes:
>
>This feels like a hardware configuration problem, but I seem to be 
>overlooking something ...  My old configuration was as follows:
>
>---on internal connect on Adaptec <----                --> on external connect
>CDC Wren IV HD --- Archive Viper Tape --- Adaptec 1542b --- Toshiba MK-156FB HD
>  id 1                 id 4                id 7                   id 0
>
>There is a termination at the CDC end and at the Toshiba end.  Everything
>worked just fine.
>
>
>I just got my Maxtor 8760S back from warranty repair, and have added it
>as follows:
>
>---on internal connect on Adaptec <----                --> on external connect
>CDC Wren HD --- Archive Tape --- Adaptec 1542b --- Toshiba  --- Maxtor
>  id 1                 id 4           id 7           id 2        id 0
>
>There is a termination at the CDC end and at the Maxtor end.
>
>I am not able to boot from my Esix floppies with this configuration.
>When I do, it gets to the secnd boot disk, then the machine hangs.
>There is a little disk activity for a minute after starting to read the
>second boot disk, but then nothing.  By removing either the Toshiba or
>Maxtor, and adjusting the termination/drive ids appropriately, everything
>is fine.    Also, with both drives in place, if I run SCSICNTL v5.5,
>it tells me "drive failed to respond to read capacity command" or some
>such thing.  The Toshiba is the culprit, it doesn't show up in the 
>"select device menu" in SCSICNTL.  Without the Maxtor in place, the
>Toshiba responds just fine!  The Maxtor responds either with or without
>the Toshiba in place.
>
>By removing a drive a ta time, I was able to format, partition, newfs, etc
>eeach drive.  Right now, they are both up and running on the system. 
>Obviously, though, there is something wrong.  If I need to boot from floppy,
>I have to reconfigure the hardware!  If I want to boot and run SCSICNTL,
>again I need to reconfigure the hardware!
>
>One side issue here is that I had a dos floppy infected with the Stone
>virus.  (THANKS to all in this conference who alerted me to that as being
>the source of the "Your PC is now Stoned" message I was getting)  By booting
>with that floppy, I wiped out my Esix boot disk and to re-install
>Esix.  Esix is booting just fine, so I guess that is OK now.  The dos
>boot disk I use now is CLEAN according to "virx.exe".  In any case, I 
>don't see how that would cause the SCSI problem outlined above (would it?)
>
>My first guess was a termination problem - but as shown above, I have
>termination at each end of the chain.  I'm a little fuzzy about whether
>each of the units should have parity-checking enabled/disabled, and
>termination power supplied to drive/bus, etc, ...  I've played with
>those a bit, and haven't seen a difference.  Maybe I haven't hit on 
>the right combination of configuration parameters???
>
>Thanks very much in advance for advice on how to cure this situation.



Have you removed the SCSI terminators from your 1542b?  Ideally, your SCSI
bus should only be terminated at the ends.  The external connector and the
internal connector are the same bus.  I have seen problems like this before.
I am using an ADAPTEC 1540A, however, I have nothing on the external connector
right now.

Rick Kelly	rmk at rmkhome.UUCP	frog!rmkhome!rmk	rmk at frog.UUCP