You may want
to compare your drive to the documentation on the
HP 88780 under bitsavers/pdf/hp/tape
These 9 track SCSI tape drives (HP 88780) were AKA 7979A, 7980A,
7980XC/SX.
The were OEMed by a LOT of manufacturers, including
IBM, Sun, Tandem,
etc.
I've never seen a Tandem that wasn't HV Differential SCSI.
A lot of them have come through BDI.
Sun-labeled ones are what you should watch for.
They all seem to have the 800bpi option, and are SE SCSI.