a small addition to willow's post....
note, you are dealing with different versions of the scsi spec, 50 pin (usually called scsi 2) vs
68 pin (not sure if this is technically scsi 3, or just transport, disk really isn't my thing(outside of fcal)) the problem/difference is the rated speed of device is different per spec/scsi version.
scsi
fast and wide scsi
ultrwide scsi
etc
an idea would be to have the older spec'd equipment further on down the chain.
host-->68pin-->50pin-->50pin+terminator
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