For SCSI terminator power (TERMPWR), only one device in the chain should be set to provide it, or terminator power should be supplied by the host, which in the case of the Mac Plus can't be done.
For hard drives, jumper settings are usually fairly easy to find. The current manufacturers of hard drives have most of the specifications for drives made by companies they bought or merged with available on their websites. For a Mac Plus, set the device plugged into the Mac to provide TERMPWR to the bus. The device at the end of the bus should be set to get TERMPWR from the bus. It also works to have the end device provide its own TERMPWR. Older devices that have resistor packs to remove to disable termination often can't provide their own TERMPWR. If the device at the end of the bus is capable of self-termination, set its jumpers or switches to enable termination. Then you don't need an external terminator. All devices between the end device and the host must have termination and termination power disabled, except of course the first device providing TERMPWR to the bus. It shouldn't bother if they are set to get TERMPWR from the bus because they have termination disabled, but it's best to have both off/disabled. I've heard the special black bus end terminator for the IIfx is not needed for later production of the IIfx after Apple changed the SCSI circuitry to work with normal passive terminators. http://support.apple.com/kb/TA42169 The IIfx and SCSI -- ----- You received this message because you are a member of the Vintage Macs group. The list FAQ is at http://lowendmac.com/lists/vintagemacs.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To leave this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/vintage-macs Support for older Macs: http://lowendmac.com/services/
