SCSI connection on PB 5300cs

The problem is probably not SCSI ID numbers, but SCSI Termination and Termination Power.

The SE has an internal SCSI Hard drive. That drive is set to provide the required 5 Volt power onto the Termination Power pin on the SCSI cable. External Terminators use this power to "pull up" the signals toward 5 Volts when they are not being driven low, effecting Termination.

The 5300 does not use a SCSI drive internally, and does not provide Termination Power onto the Bus. It predates the PowerBooks \[3400 and later models] that deliberately provide Termination Power onto the Bus.

The Zip Plus makes many (in my opinion, far too many) compromises to support its use on a parallel port -- the most grievous of which is to cut half the SCSI signals and re-drive them to the second connector, thus negating the effects of any Terminator applied to the second connector. You must either use its internal Termination switch to effect Termination, or use an "in-line" Terminator.

It is entirely possible that even with very short cables there will not be enough Termination, and that the Termination Power required will not be supplied by the Zip Drive. In that case, you may need an additional external SCSI device to supply Termination power so that an external in-line Terminator can do its job.

If this all sounds like "word salad" to you, please post more info about exactly which cables \[how many pins to how many pins] and which Terminators are used in your set-up and readers will work to get you going again.

Message was edited by: Grant Bennet-Alder

"I'll have to try hooking up a terminated hard drive after the Zip Plus; "

Do not hook up anything after the Zip Plus -- its second connector is effectively NOT a SCSI connector. To use another device it must be installed before the Zip Plus. Assume the second connector on the Zip Plus is only for a serial printer -- not for another drive and not for a Terminator.

Every other well-behaved SCSI device has a metallic connection from one end of the Bus to the other -- they never attempt to break and re-drive signals because when you do, Termination does not work.

If you have a purple Zip drive cable, it is not magical -- it is merely a 25-pin straight-through shielded SCSI cable. You can substitute any other SCSI cable as long as the connectors are the right male and female type, or you can use sex changers to get the setup you need. A Mac "System Cable" the regular 25 to 50-pin Centronics style, can be used where needed facing either direction.

Message was edited by: Grant Bennet-Alder

John,

but the 5300 (OS 7.5.2) balks on startup and displays a bouncing SCSI symbol with the currently selected SCSI number beside it

The PowerBook 5300cs appears to be in HD Target Mode (SCSI Disk Mode). This is used to connect a supported PowerBook computer (such as this one) to a SCSI desktop Mac. It means that the PowerBook would act as an external hard drive to that Mac.

I got an HDI-30 SCSI adapter

Does the adapter plug have all 30 pins (not only 29)? Unless the adapter has a switch, it will then make the PowerBook operate in HD Target Mode (SCSI Disk Mode).

In order to connect an external hard drive to the PowerBook, a 29-pin plug is needed (or a third-party 30-pin adapter with a switch set in the correct position).

Details about SCSI can be found in the manual.

Jan

Hi John,

In answer to your question, the adapter has 25 pins,

The plug that I had in mind was the square one matching the PowerBook's SCSI port.

PowerBook Setup has SCSI Disk Mode set to 5

This only means that the PowerBook, in HD Target Mode, will appear as a SCSI ID 5 hard drive to a desktop Mac.

SCSI Dock "On" must work with Target Disk mode, and that change alone probably fixed things.

Yes, that is correct. The switch "connects/disconnects" the 30th pin (which controls whether or not the PowerBook will operate in HD Target Mode).

Glad to hear that it is working.

Jan

Yes, an adapter/cable without a switch, has 30 pins in the version used for HD Target Mode (SCSI Disk Mode) and 29 pins in the one for an external SCSI hard drive (or other SCSI device).

An adapter equipped with a switch always has 30 pins (the position of the switch determines whether the adapter shall appear as a version with 30 or 29 pins).

Jan