Your Power Macintosh 8500 computer has an internal and external SCSI bus. This allows you to connect up to 12 SCSI devices. You can use the same SCSI ID number twice on the same computer as long as the duplicate SCSI ID numbers are not on the same bus.
In your case, the internal CD-ROM drive is set at SCSI ID 3 at the factory and your Syquest drive on the external bus is also set at SCSI ID number 3. This configuration works fine, however, PC Exchange does not understand multiple SCSI buses and is unable to access the second device with the duplicate SCSI ID on the external bus.
The workaround is to set a SCSI ID for the Syquest drive that is unique to both buses. After doing this, PC Exchange will be able to access the Syquest drive.
On Macintosh computers with more than one SCSI bus, another issue sometimes appars. If you use the internal fast-SCSI bus, PC Exchange show multiple devices for the same device. For example a third-party hard disk may be shown in PC Exchange as ID 0 and 0.1
Apple Engineering is aware of these issues. Multiple bus support will be added to a future version of PC Exchange.
Article Change History:
14 May 1996 - Added fast-SCSI devices showing up with multiple SCSI IDs.