I've got a 3 different tape drives I'm testing here, an internal LTO-2, external quantum LTO-3 and a sony external AIT-5 drives.
I've got 2 LSI and 1 adapter PCI-e SCSI controllers
It doesn't matter what cable, terminator or controller I use, the drives are always detected as narrow 40MB instead of 80/160/320MB 16bit. I've tried a lot and so far no difference. The scsi controllers ave very little configuration.