As you have already deduced there are different sizes. ATA/IDE drives do use jumpers for selection of Master, Slave and Cable Select when it is necessary, and they use the wider 2.54-mm units.
SCSI drives generally use the 2-mm jumpers unless there is an attached adapter for SCA (80-pin) to 68-pin or 50-pin, or 68-pin to 50-pin kludging. (It works, but it is a compromise that needs care in the doing.) Elsewhere, as for enabling termination, motor start, start delay, parity enable/disable, write protect, termination power supply and anything that I have forgotten, 2-mm jumpers of various heights (to fit the available spaces around the drives) are used.
Parity, write protect, motor start and spin-up delay are either not often, or never, of concern with HDDs in Macs. As a generality, older Quantums need no jumpers. Their termination resistors are physically removed if necessary, and only SCSI ID=0 is acknowledged. Later, but still old, HDDs allowed for SCSI ID selection (in case of additional drives in the daisy-chain) with three jumper pairs, and a pair for enabling termination (by means of on-board ICs) if necessary.
Modern drives vary greatly in jumpering needs depending on the make of HDD. Again as a generality, Macs are likely to need TE (if physically last on the cable), TP (which can come from the drive or the bus) to power the termination circuits and MS drive start, and disabling of funny-bugger features (eg IBM drives) such as unit attention and sync. negotiation. Jumper patterns for their HDDs are published by most manufacturers, even for old drives. If you can't find what you need, post what you have on your drives and someone will advise you.
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SCSI drives generally use the 2-mm jumpers unless there is an attached adapter for SCA (80-pin) to 68-pin or 50-pin, or 68-pin to 50-pin kludging. (It works, but it is a compromise that needs care in the doing.) Elsewhere, as for enabling termination, motor start, start delay, parity enable/disable, write protect, termination power supply and anything that I have forgotten, 2-mm jumpers of various heights (to fit the available spaces around the drives) are used.
Parity, write protect, motor start and spin-up delay are either not often, or never, of concern with HDDs in Macs. As a generality, older Quantums need no jumpers. Their termination resistors are physically removed if necessary, and only SCSI ID=0 is acknowledged. Later, but still old, HDDs allowed for SCSI ID selection (in case of additional drives in the daisy-chain) with three jumper pairs, and a pair for enabling termination (by means of on-board ICs) if necessary.
Modern drives vary greatly in jumpering needs depending on the make of HDD. Again as a generality, Macs are likely to need TE (if physically last on the cable), TP (which can come from the drive or the bus) to power the termination circuits and MS drive start, and disabling of funny-bugger features (eg IBM drives) such as unit attention and sync. negotiation. Jumper patterns for their HDDs are published by most manufacturers, even for old drives. If you can't find what you need, post what you have on your drives and someone will advise you.
de