[T Reisig]

Is there a limit to the number of SCSI devices that can be hooked up to a Macintosh? A friend has been trouble shooting his SCSI prob's and found if he excedes a certain number (7 I think) of external SCSI drives formatted with non-Apple drivers that his computer won't boot.
I was running into a similar issue on a system at my work (4-18 gig cheetah's, 2-23 gig Glyph's, and a DDS-4 tape backup on an Atto dual Ultrawide PCI card), but attributed it to a bad bay in my expansion tower.
Is there a known limit to how many drives you can run?

Tim

[elzinat]

yes, there is a limit. The SCSI chain can have at most 8 devices; each has a device ID between 0 and 7. Since the Computer Itself is always ID 7, you can have at most 7 other devices. If you have more than 7 other devices on the chain at the same time, the Pigeonhole Principle guarantees that there will be at least one instance of two devices with the same ID. This causes great unhappiness for the SCSI controller card and the boards in the devices which have the duplicate IDs, and bad stuff happens. Don't do it!

[T Reisig]

elzinat,

Thanks for your reply. To further clarify:
I'm aware of the SCSI ID limitation. In this situation we're
both using DUAL SCSI cards and not doubling
device ID's. Further troubleshooting has determined that if all
drives are formatted with Apple drivers (w/Drive setup), all is well. The trouble arises when external drives are formatted with differant drivers.

Tim