SCSI - A Quick Handy Guide



SCSI Technical Note


This Document describes briefly the rules governing SCSI. For more detailed information see the SCSI Set-up Guide.


Depending on how you decide to operate S/LINK - "on-line" or "off - line" or both - your SCSI configuration will be different. There is no specific way that you must connect your devices, however you must follow several rules to assure consistent SCSI operation:


1. SCSI cabling must not exceed 6 metres (19.5 feet). The shorter the better. Remember that there is some length of cable inside the machine as well.  You may need to make some new cables to enable you to connect to the Mac.

See the SCSI Set-Up Guide for details on the SCSI Sentry.


2. SCSI cabling must form a chain. T's are not allowed except for short ones.


3. Both ends of the SCSI chain must be terminated. The Mac terminates one end. The D24 card in your Synclavier or PostPro terminates the other. If you have a MacIIfx, then you have a special terminator that was supplied with the machine by Apple. If you have a DTD slaved to your Synclavier, you may need to unterminate the DTD's D24 card. This requires a modification to the card, and may require some recabling.


4. There can be no duplicate ID's on the SCSI buss. The following devices have fixed ID's and must not be used by any other device when they are on the buss.


                                           ID 1:                Optical Drive (12" or MO)

                                           ID 3:                Direct-To-Disk Computer

                                           ID 5:                W0:

                                           ID 6:                Synclavier Computer

                                           ID 7:                Macintosh Computer


If any of the above are not present on the SCSI bus, then its ID is free for use by other devices.


"Off-line" Direct-To-Disk drives can have any ID. The drives can be in any order. (S/LINK knows which drives are 1, 2 and 3 etc.), but the drives must have been already formatted in the DTD.

For "On-line" operation, the DTD drives are on  seperate SCSI chains in the DTD and are managed by the DTD computer, so they have no effect over the Mac SCSI ID's at all.


5. Only one device on the bus should supply termination power. The Mac supplies termination power, so turn off any other devices termination power. The D24 in the Synclavier has a link to turn off Termination power close to the 50 way SCSI connector on the card.


You may hook up your SCSI devices in any order you likeas long as you follow the rules above. Mac one end, Synclavier the other, everything else inbetween.


The Synclavier and DTD will not show up with S/LINK unless they are running Release 3.2. Your Synclavier should be powered up and booted before the Mac so that they do not hold the SCSI bus down.