neese@adaptex.UUCP (02/21/90)
>A SCSI bus consists of a 50 pin bus running from a SCSI controller. >Bus lenght can be up to 15 feet. >On this bus you can have up to 8 devices. >Connectors for getting on the bus come in many different flavors, >(Centronics style, AMP-socket connectors, D style connector) >Some SCSI peripherals provide a bus extention to allow the bus to >continue on to the next device. This is simply a parallel extention of the bus. > >so far so good? > >Where must a SCSI bus be terminated? Only once, and at the last device on >the bus would seem to be the logical choise. No. A SCSI bus must be terminated at each end of the cable. If the cable starts inside a computer and, via an external connector, exits to the outside world and connects to a device, then the terminators must be removed off the adapter and the bus would be terminated at both ends of the cable. >When taping into a SCSI bus, the tap or stub lenght can only be a few >inches in lenght i guess? But can you get away with a longer stub lenght >if you also terminate that specific device? A stub is not a good idea. This leaves you open to all kinds of unreliable operations. If you have a controller that supports a number of LUN's, then termination of those LUN's are handled independent of the SCSI bus. The controller itself is the only main concern. >confirmation/correction of the above would be greatly appreciatted, and >any other cabling/hardware tips also welcome. (a tip on a good hardware >reference book also welcome). Don't know of any good books. But if you stick to terminating the SCSI bus at both ends of the cable (SCSI bus), then you will be okay. Roy Neese Adaptec Central Field Applications Engineer UUCP @ {texbell,attctc}!cpe!adaptex!neese merch!adaptex!neese uunet!swbatl!texbell!merch!adaptex!neese