A generous customer gave me an old Compaq 7 disk array and a single port UltraSCSI module to troubleshoot some RAID5 configurations, here are the switch options to set provided by Alex Daniels.
Module: DS-BA35X-FA is a Single port, single-ended UltraSCSI personality module
for BA356. Although these settings cover the single or dual
It has two sets of switches as you have observed (S3 and S4).
S3 (SCSI Address switch) – When shelf bus address switches on shelf one are all set to OFF, then the SCSI bus IDs are 0 through 6 on the first shelf.
When shelf bus address switches 1, 2, and 3 on shelf 2 are set to ON, and 4,
5, 6, and 7 are set to OFF, then SCSI bus IDs are 8 through 14.
S4 (Bus termination switch) – 1,2 are for Channel A. 3,4 are for Channel B
1 OFF or 3 OFF – 16 Bit External Bus Termination
Terminates all SCSI bus bits (full termination). This configuration is used when the shelf is the end point in a SCSI bus and terminates all signals.
1 ON, 2 OFF or 3 ON, 4 OFF – 8 Bit External Bus Termination
Terminates only the upper 8 data. This configuration is used when the input bus is a wide (16-bit) bus and it continues as a narrow (8-bit) bus. This could be used with a tri-link to a narrow device.
1,2 ON or 3,4 ON – External Bus Expansion
No termination on the shelf. The shelf is not an end point of a SCSI bus segment and no termination is needed.