Adaptec USB2Xchange User Guide - Page 34

Understanding SCSI Understanding SCSI SCSI (pronounced "scuzzy") stands for Small Computer System Interface. SCSI is an industry standard computer interface for connecting SCSI devices (such as a hard disk drive, CD-ROM drive, or scanner) to a common SCSI bus. A SCSI bus is the path or channel that connects your computer, USB2Xchange adapter, and one or more SCSI devices. It's not a physical object that you can point to; instead, it's the whole collection of SCSI cables and devices (including the USB2Xchange) that make up the communication channel. The size of the bus grows when more devices are added. When there is activity on the SCSI bus, the LED on the top of your USB2Xchange flashes. For the SCSI bus to function properly, each SCSI device must have a unique SCSI ID and must be correctly terminated. For more information, see the next section (Preparing SCSI Devices for Installation). Preparing SCSI Devices for Installation When preparing to install SCSI devices, make sure to: I Check the SCSI IDs. Ensure that the USB2Xchange adapter and each SCSI device you want to connect to it has a unique SCSI ID. See the next section, SCSI IDs, for more information. I Use only high-quality SCSI cables to ensure reliable data transfer. See Using SCSI Cables on page 26 for more information. I Terminate the ends of the SCSI bus. See Terminating the SCSI Bus on page 25 for more information. SCSI IDs SCSI IDs identify each device on the SCSI bus and determine priority when two or more devices are trying to use the SCSI bus at the same time. The SCSI card is also identified by a SCSI ID. For the USB2Xchange adapter, SCSI IDs are numbers between 0 and 7. Adaptec presets the USB2Xchange to SCSI ID 7. You cannot change this setting. SCSI ID 7 has the highest priority on the SCSI bus; the remaining SCSI IDs descend in priority from 6 to 0. Use SCSI ID 0 for the first SCSI hard disk drive. 24