NMR - SCSI interference ???

Finn Drablos (drablos@marvin.mr.sintef.no)
Mon, 22 Nov 93 11:32:26 +0100

I am responsible for some of the computer systems in an NMR center. In
particular I am responsible for two Silicon Graphics workstations used
for NMR processing an molecular modelling. For two of the systems, a
Personal Iris and an Indigo2, we have problems with write errors and
bus resets during write operations to SCSI tape drives (during backup).
There is never any problem during normal disk access, only during tape
write, where it seems to happen 1-2 times every hour during normal
backup (which obviously is not normal anymore). For a long time we
belived that this was a hardware problem with our Personal Iris, but
recently we installed a new Indigo2, and got exactly the same type of
problems there. And as both workstations have some external SCSI cable,
and as we believe the the problems first were observed on the Personal
Iris after installing some new hardware that made the external SCSI cable
necessary, we started to think about the possibility that this setup may
pick up external noise through the SCSI cable, especially from the NMR
instruments. The building is virtually filled with NMR instruments,
500MHz, 200MHz and Biospec Bruker instruments, and two Philips instruments
for medical imaging. However, our suspect at the moment is the 500 MHz
Bruker instrument located approx. 10 meters from the computers.

So my question is : Has anyone seen any kind of problems similar to this?
And do you believe that standard SCSI cables can pick up noise from
any NMR experiments? Especially after the announcement of the
ASPECT 300 SCSI interface I feel that this is a very relevant question.

Regards,

Finn Drablos drablos@marvin.mr.sintef.no
MR-Center, SINTEF UNIMED phone +47 73 99 77 10
N-7034 TRONDHEIM, NORWAY fax +47 73 99 77 08