Problem with Cipher 1/2" drive on 472 controller

[John Gibbins]

A neighbouring site has a Cipher 990M front loading 1/2" tape drive which
has been running on a Xylogics 772 controller.  As Sun does not support
the 772, they are trying to downgrade the controller to a Xylogics 472
controller so as to be able to use the drive at 4.1.  They had a third
party device driver for the 772 at 4.0.3, but this is not available for
4.1[.1].  When they replaced the controller, any dump tapes they wrote
were unreadable.  Any tapes written on the 772 controller could be read
fine.

After playing around for a while I discovered that if you write to a tape
with a small block size eg 32 (ie 16kb) and then write with a large block
size (64+), it was possible to write/read dump tapes (dump was used with
block size of 126).  This method was not always reliable.  We tried
swapping the 472 with another one: same problem.

We found another site that also was running SunOS 4.0.3 on a Sun 3/160
with a 472 and Cipher (although it was a Cipher F880 not 990) drive.  Our
tests showed that they had the same problem.

Is anyone else  running a Cipher drive on a 472 controller?  Have you seen
this problem and know anything about?  If so please HELP!!!!  If we don't
find a solution, we will have to put back the 772 and never advance beyond
4.0.3!

Please mail as I am a slow news reader.
John Gibbins
GPO Box D184                              Internet: johng at uniwa.uwa.oz.au
PERTH  W.A. 6001                          Phone:    61-9-3408547
AUSTRALIA                                 Fax:      61-9-3883414