The usual rule of thumb applies:
1.) Internal SCSI drives (most of them) have the SCSI termination already built-in on their controller cards. So you only need to make sure termination is enabled on those type of drives. Usually there's only 1 internal hard drive in each retro Mac, but there are configurations of more than 1 internal HDD, plus add in if there is 1 or more internal CD-ROM drives.
2.) For external SCSI devices, you usually want termination enabled at the beginning and at the end of the SCSI chain. Some devices, like storage drives, are finicky and work best with just a terminator at the end of the chain, rather than adding one at both ends. For this, it takes some trial and error to get SCSI working right.
3.) This regards the SCSI id number assignments. ID #7 is reserved for the Mac itself. Internal hard drives are assigned ID #0 and the internal CD-ROM (if you have one) is assigned ID #3. That leaves you ID # 1, 2, 4, 5 and 6 for anything else you add on. I've had good luck assigning #2 or #6 for external drives. The most critical rule is to make sure you assign a different ID number for each device; you should never assign the same number to 2 SCSI devices or your Mac will crash.
4.) Check the quality of your SCSI cables. Cheaply built cables will have problems with shorting out and also aren't shielded properly; RF interference and other noise can leak in and cause problems sending and receiving across that cable. Also, make sure you use short length cables. Even though the standard is up to 18 feet of cable, you do need to subtract from that figure the length of cable inside an external device's case.
5.) Make sure you turn on your external SCSI devices before powering up your Mac. You might be able to leave unused SCSI devices turned off, but read the manual or test it to see if it can allow pass-through while turned off.
6.) Hook up your SCSI devices in a different sequence in the chain. This can be one way to fix certain problems of SCSI voodoo. If you do this, make sure you move the termination configuration for the end of the chain from one device to the new end device. Don't try to terminate devices in the middle of the chain.
Give this a whirl and let us know how it works for you.
73s de Phreakout. :rambo:
1.) Internal SCSI drives (most of them) have the SCSI termination already built-in on their controller cards. So you only need to make sure termination is enabled on those type of drives. Usually there's only 1 internal hard drive in each retro Mac, but there are configurations of more than 1 internal HDD, plus add in if there is 1 or more internal CD-ROM drives.
2.) For external SCSI devices, you usually want termination enabled at the beginning and at the end of the SCSI chain. Some devices, like storage drives, are finicky and work best with just a terminator at the end of the chain, rather than adding one at both ends. For this, it takes some trial and error to get SCSI working right.
3.) This regards the SCSI id number assignments. ID #7 is reserved for the Mac itself. Internal hard drives are assigned ID #0 and the internal CD-ROM (if you have one) is assigned ID #3. That leaves you ID # 1, 2, 4, 5 and 6 for anything else you add on. I've had good luck assigning #2 or #6 for external drives. The most critical rule is to make sure you assign a different ID number for each device; you should never assign the same number to 2 SCSI devices or your Mac will crash.
4.) Check the quality of your SCSI cables. Cheaply built cables will have problems with shorting out and also aren't shielded properly; RF interference and other noise can leak in and cause problems sending and receiving across that cable. Also, make sure you use short length cables. Even though the standard is up to 18 feet of cable, you do need to subtract from that figure the length of cable inside an external device's case.
5.) Make sure you turn on your external SCSI devices before powering up your Mac. You might be able to leave unused SCSI devices turned off, but read the manual or test it to see if it can allow pass-through while turned off.
6.) Hook up your SCSI devices in a different sequence in the chain. This can be one way to fix certain problems of SCSI voodoo. If you do this, make sure you move the termination configuration for the end of the chain from one device to the new end device. Don't try to terminate devices in the middle of the chain.
Give this a whirl and let us know how it works for you.
73s de Phreakout. :rambo: