How to set a new SCSI number for a second drive?

The three or four straps labeled ADDR0, ADDR1, ADDR2, and possibly ADDR3 encode a binary unit number. installing a strap on the

ADDR0 adds 1,
ADDR1 adds 2,
ADDR2 adds 4,
ADDR3 adds 8.

Then just add them up to get the unit number.
Example: ADDR2 adds 4 + ADDR 0 adds 1 to yield unit 5

Avoid 7 (controller) and 3 (internal CD). Factory boot drive is typically unit 0.

IBM has sold its drive business to Hitachi. The jumpers/straps for that drive are available on the Hitachi Global Storage Technology website here:

http://www.hitachigst.com/hdd/support/dpes/dpesjum.htm

Remember that only the last drive on the cable should have the termination jumper/strap installed, so that when you put BOTH drives on the cable together, the "middle" one must have its termination jumper/strap removed.

The "straps" are the little plastic things that connect a pair of "pins." I call them jumpers. Hopefully, you have one extra available.

Usually, if you don't have any jumpers on the first three sets of pins, the ID is 0. The primary drive on a Mac is usually ID 0. The CDROM drive is usually set to ID 3. If you put a second drive inside the Mac, and you have no external SCSI devices, the best thing to do is put just one jumper on the first set of pins. This should give you ID 1. Then, you will have IDs 0, 1, and 3 used, and that should work fine. ID 7 is used by the Mac CPU, so don't use it.

Later, if you add any external SCSI devices, avoid using those ID numbers.

Walter,

This web site gives a good diagram:

http://www.hitachigst.com/hdd/support/dpes/dpesjum.htm

On a Quantum hard disk drive - they were the original equipment manufacturer (OEM) hard drive provider for Apple, you will see three or four pairs of pins on the green circuit board. They are labled:

AO . .
A1 . .
A2 . .

If no pins are connected, you have SCSI ID Zero This was the standard setting from the factory.
If you short out the pins beside AO .__. , you have designated SCSI ID One.
If you short out the pins beside A1 .__. , you have designated SCSI ID Two.
If you short out the pins beside A2 .__. , you have designated SCSI ID Four.

These values can be added together to get other SCSI IDs. If you have a jumper beside AO AND A1, that will add up to SCSI ID Three.

Some of the quantum drives used tiny black plastic jumpers with tiny metal contacts. I have yet to find a store that sells the tiny ones. I get my larger jumpers from old PC motherboards that are being thrown away. A small piece of aluminum foil will work as a jumper in a pinch. Just make sure it soed not fall off and short something else out!

Jim

PS
CD-ROM drives are set at the factory as ID 3. Internal drives are set at ID 0. I set my external SCSI drive at SCSI 1 so it does not conflict with the internal drive. Internal Zip drives are set at ID 5 and external Zip drives let you choose between 5 and 6. I set my burners at ID 4. Come up with a master plan for your devices like scanners and burners. Apple System Profiler will give you info on the device ID. If the computer fails to boot, turn off all but one SCSI device and make sure of its ID. Then check each subsequent device by powering up only one device at a time while booting from a CD at ID #3.