6.4 Installing an FDD

Installing an FDD in all but the newest systems is straightforward. Note, however, that some cases designed to accept FlexATX motherboards have only one externally accessible 5.25-inch drive bay, intended to accept a CD or DVD drive. This is because FlexATX systems are intended to boot from CD and so eliminate "legacy" connectors, including the FDD. That means if you intend to install an FDD in a FlexATX system, you'll need a case with two or more externally accessible drive bays (assuming you also want to install an optical drive and/or tape drive in the system), and you'll need to buy a separate PCI card that provides an FDD interface because FlexATX and other "legacy-reduced" and "legacy-free" motherboards do not provide an embedded FDD interface.

FlexATX motherboards also fit standard ATX cases, so installing the FlexATX motherboard in a standard ATX case eliminates the drive bay problem, although not the lack of an FDD interface. If you really need an FDD in a system, we recommend using a motherboard that provides an embedded FDD interface.

Use the following rules when installing FDDs:

To install one FDD in a system, standard practice is to jumper that drive as the second drive (DS1/DS2) and connect it to the end connector. Alternatively, you can jumper the drive as the first drive (DS0/DS1) and connect it to the middle connector. Either method allows the system to see that drive as A:. If your drive cable has only two connectors, jumper the drive as the second drive (DS1/DS2). Note that most current 3.5-inch FDDs are set permanently as the second drive, and have no jumper to allow changing that assignment. Such drives work properly with a two-connector data cable, and should be connected to the end connector on a three-position data cable.
To install two FDDs in a system, jumper both drives as the second drive (DS1/DS2). Connect the A: drive to the end connector and the B: drive to the middle connector. (Note that the chipsets used in many recent systems support only one FDD.)
Sometimes, cable constraints (length or available connector types) make it impossible to configure the drives as you want them. If this happens, check BIOS Setup to see if it allows you to exchange A: and B:, overriding the drive designations made by DS jumper settings and cable position.

To install the FDD, take the following steps:

Before you start, examine the drive to verify the location of Pin 1 on the data connector because it may be impossible to determine which is Pin 1 once the drive is installed in the computer. Most drives use an unshrouded and unkeyed connector, many of which are very poorly labeled. Some do not label Pin 1 at all. On all such drives we have seen, Pin 1 is located nearest the power connector. Better drives use a shrouded and/or keyed connector such as that shown in Figure 6-4, and are a better choice.

Figure 6-4. An NEC 3.5-inch FDD, which uses a shrouded cable connector rather than the typical bare pins (note the missing pin at lower left, which keys the connector)
Once you have located Pin 1 on the drive, connect the FDD data cable to the drive, aligning Pin 1 on the cable (the side with the red stripe) with Pin 1 on the drive. Do this before you install the FDD in the drive bay, particularly if you are using a drive with an unshrouded data connector. Otherwise, it's very easy to install the data cable offset by a column or row of pins. We know because we've done it frequently. Be very careful when installing the cable because it's quite easy to bend pins on an unshrouded connector. Once you're sure the cable is aligned properly with the connector, place your thumb in the middle of the cable connector, as shown in Figure 6-5, and push gently on the cable connector until it seats fully.

Figure 6-5. Connecting the cable to the FDD, with Pin 1 oriented properly and all pins aligned
In most cases, the FDD installs from the front, but in some cases it installs from the rear. If the drive bay requires installing from the front, slide the FDD into the bay, using your free hand to feed the cable through without kinking it, as shown in Figure 6-6. In most cases, you must leave the FDD projecting half an inch or so in front of the metal chassis so that the FDD bezel will align properly with the case bezel once it is installed. Most 3.5-inch FDD bays have round screw holes positioned properly to ensure that everything aligns once the case bezel is replaced. Some, however, have elongated slots rather than round holes. On these cases, you may have to align the FDD by trial and error.

Figure 6-6. Sliding the FDD into the drive bay, making sure the cable feeds smoothly into the case interior
Once you have properly aligned the screw holes in the drive bay with those in the drive, insert the screws and tighten them until they are fully seated. Do not overtorque the screws. The number of screws required and their positions depend upon the particular FDD and case. Most FDDs and cases allow you to install as many as eight screws?two in front and two in back on each of the two sides. That's complete overkill. We generally use four screws, top-front and bottom-back on each side. Some cases make it very difficult to install screws to support the right side of the FDD (as you face the front of the case). In such cases, we generally install screws in all four positions on the left side of the drive and leave the right side unsupported. If your case is one that requires trial-and-error alignment to get the front of the FDD lined up with the front of the case, insert only two screws initially and tighten them down only enough to allow the FDD to slide in or out with some resistance. Then, replace the front system bezel, get the FDD aligned just right, tighten the two screws you already installed, and then install the remaining screws. If you're a belt-and-suspenders person, place a small dab of nail polish on each screw head to prevent it from vibrating loose.
With the drive securely fastened to the chassis, connect the power cable to the drive, as shown in Figure 6-7. The power cable and connector are keyed, and so can fit only in the proper orientation. But be careful to align everything properly before you press the connector into place. Some drives use fragile pins on the power connector, and we've bent more than one set when attempting to connect power to an FDD in an awkward situation, such as working under a desk in near darkness.

Figure 6-7. Connecting the power cable to the FDD, making sure the connector is aligned properly with the pins