cfj@isc.intel.com (Charlie Johnson) (11/20/90)
I was wondering if anyone out in Usenet has seen a problem similar to this. We
a MDB Systems, Inc. Data Shuttle 2000 (a removable disk subsystem.) which is
configured for SCSI and has 2 Maxtor 8760 disk drives installed. In addition
to the Data Shuttle, an Exabyte 8200 tape drive has been installed on the
same SCSI string with the tape drive being the terminated device at the
end of the cable. Our initiator uses a NCR 53C90 SCSI chip as the interface
to the SCSI bus. The problem is, when we have the tape connected, during a
32K transfer to the disk drive, the drive keeps asserting DATAOUT phase even
though all the data has been transfered. The tape drive is not being accessed.
If we remove the tape drive and terminate the Data Shuttle, the 32K transfer
works fine. (i.e. After the data transfer is complete the drive goes into
MSGIN phase.) Has anyone out there seen anything like this ??
There seems to be some possibilities:
1. The Exabyte's termination circuit is bogus. (I'm just a software hack,
so I can't tell.)
2. The Data Shuttle creates a stub which is too long.
3. Device driver bug. (Always possible.)
4. Other weird hardware interaction.
It doesn't appear that we are exceeding the SCSI cable length limit. Also, if
I connect a PED 4000 SCSI analyzer, then everything works fine. (Kind of like
quantum mechanics.)
I know this is long winded, but I'm stumped.
Thanks!!
--
Charles Johnson
Intel Corporation, Supercomputer Systems Division
15201 NW Greenbrier Pkwy
Beaverton, OR 97006 phone: (503)629-7605 email: cfj@isc.intel.com