DSSI is CI. It is a networking protocol. Youre not directly talking to 
media devices, but to HSC's thathappen to exist in the logic board in the 
disk unit. The SHAC is a CI adaptor on a chip that uses DSSI as its
physical layer for communication. 
The communication with the DSSI disk is MSCP over CI. I think it would 
make sense to support the SHAC as a CI adaptor and then run the regular 
MSCP driver over it instead of the Qbus. 

Nexus - UBA - Qbus - Disk controller - Disk 
Nexus - SHAC - CI (DSSI) bus - disk controller (on disk) - disk

Ultrix for example treats DSSI this way. it uses the ra driver for them, 
thru ci, using a port driver for the shac to present CI. 


isildur