Adaptec SBC-596, SBC-599 manual Scsi Terminators

The AIC-7880 supports the SCSI Configured AutoMatically (SCAM) protocol, which assigns SCSI IDs dynamically and resolves SCSI ID conflicts automatically at bootup. If your system includes SCSI disk drives or other devices that support SCAM, you do not need to manually assign SCSI IDs to these devices.

Most SCSI devices currently in use, however, do not support SCAM. The SCSI IDs on these devices must be set manually. To change the SCSI IDs on these devices, refer to the device’s documentation.

If you install more than one SCSI host adapter in the computer, each adapter forms a separate SCSI bus. SCSI IDs can be reused as long as the ID is assigned to a device on a separate SCSI bus (e.g., each SCSI bus can have a device with SCSI ID 0).

SCSI Terminators

To ensure reliable communication, the SCSI bus must be properly terminated. Termination is controlled by a set of electrical resistors, called terminators. Terminators must be placed (or enabled) at the two extreme ends of the SCSI bus. All devices that lie between the ends must have their terminators removed (or disabled).

Termination on the Ultra Wide SCSI itself is controlled by software commands via the SCSISelect utility. The default setting is set to Automatic. When set to Automatic, if the AIC-7880 detacts that SCSI cables are connected to any of its two SCSI connectors, it automatically sets the termination setting for the low and high bytes of the 16-bit Wide SCSI bus. The low byte controls 8-bit SCSI; the low and high bytes together control 16-bit Wide SCSI.

Chapter 6 SCSI Setup and Configurations 65