Some flop~y drives require configuration before they are installed. Configuring a floppy drive requires two steps at most:

(1) Setting the correct drive select number and
(2) Terminating the floppy drive system.

The drive select setting is a number assigned to a drive that enables the controlling circuits to distinguish between two floppy drives. Some drives have the drive select setting already configured and it cannot be changed. But if a drive has a drive select setting, a technician assigns a drive select number to the drive by placing a plastic jumper over two pins. Having documentation for the drive is best at this point (but not very common). Drive select jumpers are normally found at the bottom rear or at the very back of the floppy drive.

Floppy drives can have up to four drive select numbers. They are normally labeled Drive Select numbers 0, 1, 2, or 3 or Drive Select numbers 1, 2, 3, or 4. The floppy drive manufacturer determines how to label the drive select numbers. Each floppy drive that connects to one floppy cable must have a separate drive select number. Notice how both drives shown in Fig.FD-5 have the jumpers over the second drive select. It does not matter how the drive select numbers are labeled. The second drive select ~ay be numbered 1 or 2; but it is still the second drive select position. Floppy drives come from most manufacturers pre-set to- the second drive select. The original cabling for floppy drives had a lot to do with why the drive select jumper is set ,to the second position. Fig.FD-6 shows a common floppy drive cable.

Notice in Fig.FD-6 one end of the floppy cable is labeled "Motherboard Connector" This end plugs into either the motherboard or to an adapter. There are four connectors shown in the figure that can be used to attach to drives. The connector labeled 3.5 Drive "A" Connector is used to connect to the A: drive. One of the connectors, labeled 3.5" Drive B Connector, is used to connect to the B: drive. Older floppy drives used a card edge connector, whereas newer drives use a pin connector. The number and type of connectors available on a floppy drive cable varies between manufacturers. Also notice the twist in the cable shown in the figure just after the connector labeled 3.5 Drive "A" Connector. This twist is important when dealing with drive select settings.



The twisted cable physically moves the drive select jumper position from the second position to the first position by crossing a few wires. Therefore, you can connect two floppy drives to this cable. The drive connected to the 3.5 Drive "A" Connector, is seen by the computer as drive select first position, The drive connected to the middle connector is seen as drive select second position. The controller can now distinguish between the drives even though they are both set to the second position drive select.

The operating system assigns drive letters to each drive detected. The drive at the end of the cable is the A: drive and is set to the second drive select number, but is seen as drive select first position due to the twist in the cable. Drive A: always connects to the last connector on the cable. The drive connected to the middle connector, which is also set to the second drive select number, is assigned B: by the operating system.

Not all manufacturers use floppy cables with a twist before the last connector. Cables without the twist are straight-through cables. If a system has a straight-through cable, set the A: drive to the first drive select number and the B: drive to the second drive select number and the controller can tell the difference between the drives.