Summary: SBus expansion on a 670 MP (REVISION)

From: Gerald Justice (
Date: Fri Aug 13 1993 - 06:06:31 CDT

Well, I had jumped the gun. As far as we are concerned the SBus
expansion (X171A) does not work with our configuration and I have to
assume it is a problem of the devices we have exceeding the performance
limits of the SBus expansion (and unfortunately) it degrading
ungracefully (i.e. crashing) in response.

Shortly after I sent the summary (July 12--"how time flies when you are
having fun!") indicating the device worked, the system crashed again.
We did more experiments and we came up with a reliable crash "trigger"
which unfortunately is extremely unique to our site. (When a user did
a tar of a particular directory to an 8mm tape drive it would reliably
crash the system at the same place (in the list of tar files). When
one of the 8mm drives was moved to an SBus adapter that was NOT in the
SBus expansion it would no longer crash the system. (Note that copying
the relevant part of the directory to other hosts or directories and
tarring the copy ALSO crashed the system. We did fsck everything to
make sure the filesystems were not corrupt. We also sometimes got the
system to crash when tarring a similar directory (in file type and
sizes) but it was not consistent. Since the crash ratio of the SBus
expansion being in to being out was something like 100 to 1 no other
conclusion seems acceptable. Only supported SBus cards were used in
the SBus expansion.

We are sending the SBus expansion back to the dealer and will be
looking at expanding in the future either by upgrading the 670 to
something else (which we cannot afford) or by adding other hosts to
offload specific functions from the 670.

I will not repeat the original query here, it was included in the
original summary sent July 12.

Happy non-expandable computing!

Gerald Justice
Unix Systems Manager

Phone: (604) 363-0055 PDT Fax: (604) 363-0045 Telex: 049-7295
Internet: Mail: Dominion Astrophysical Observatory
                                            National Research Council (Canada)
BITNET: justice@nrcdao 5071 W. Saanich Road
                                            Victoria, B.C. CANADA V8X 4M6

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