Floppy Disk Drives

Floppy Disk Drive (FDD)- FDD saves information in a magnetic medium. The information is stored on a removable and easily transportable floppy disk. A drive that reads or writes, to separate diskettes which the user inserts. Information is stored on the diskettes themselves, not on the drive

· Floppy drives come in a variety of shapes, sizes and capacities.

In 1972, IBM developed the first floppy disk drives for its System 370 machines. These drives used 8-inch floppy disks. Other companies, such as Wang, adapted the same basic design for its dedicated word processing machines used in the 1970s and 1980s. The actual disks came pre-formatted, and only worked on a given operating system or computer. This resulted in high-cost drives and reduced the ability to use floppies as a quick means of transporting files from one system to another. When IBM introduced the personal computer (PC) in 1981, it came standard with a 5.25-inch floppy disk drive. Floppy disks were included in PCs before hard disk drives, mostly out of economic considerations. The cost of an early PC hard disk drive was more than the total cost of a system today and took half of a day to prepare and install. Some very old PCs may have a 5.25-inch drive installed. The only reason a newer machine might need one is to maintain compatibility with an old program or data stored on such disks. Today's 3.5-inch floppy disks are made of flexible plastic and coated with a magnetic material. To protect the disk from dust and physical damage, it is packaged in a plastic or coated paper case. The main reason for the popularity of floppy disk drives and disks is that they provide inexpensive read/write (R/W) removable media. The data stored on a floppy disk can be moved from one computer to another, provided both have the same type of drive. In general, it is a good idea to protect your data by always keeping two copies of any data file that you create (the original and a backup), and the floppy disk is an excellent medium for backing up, storing, or distributing copies of relatively small files, such as word processing documents.

The following table describes various floppy disks and their capacities.

The only major differences between the 5.25-inch and the 3.5-inch disk drives (other than physical size) are that the 5.25-inch drive has a slot connector and the 3.5-inch drive has a pin connector for engaging and spinning the disk, and they use different power plugs and voltages. All floppy disk drives (as shown below) are connected to the motherboard's external data bus by a 34-lead ribbon cable, shown in Figure 9.2. This cable has a seven-wire twist in lines 10 through 16. This ensures that when two floppy disk drives are attached, the drive-select and motor-enable signals on those wires can be inverted to "select" which drive becomes the active target. The remaining wires carry data and ground signals. The connector end of the cable with the twist always goes toward the drives.

Floppy disk drive cable with a twist

Early PC BIOS logic was developed to recognize one or two floppy disk drives. In such systems, no more than one 34-pin cable for floppy disk drives can be installed in the computer without resorting to special hardware. When a floppy disk drive is installed on the end connector (near the twist), the drive is logically designated as the first or primary or A drive by the BIOS. The drive attached in the middle of the cable is always the secondary or B drive. The BIOS will not recognize a B drive unless an A drive is physically installed. The number 1 red wire must be connected to the number 1 pin on the drive. If this is not correctly installed, the drive will not work (although no permanent damage can be done by installing the connector backward).

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If you install a new drive and notice that the indicator light comes on and stays on, the cable is most likely backward. The power connection for a floppy disk drive is either the large, Molex-type connector on the 5.25-inch drive or the smaller mini connector on the 3.5-inch drive. Older power supplies may only have the Molex connections, and you will need an adapter to attach a 3.5-inch drive. Newer power supplies, and all power supplies for the ATX-style cases, should have both Molex and the two-strand connection for providing a 5-volt power connection to the 3.5-inch drive. See detailed on power supply discussion. After you physically install a floppy disk drive, you need only use the BIOS Setup program to adjust the proper CMOS (complementary metal-oxide semiconductor) settings for the type and position (first or second), and the installation will be complete. In CMOS setup, select the drive (A or B) and enter the correct capacity.

NOTE

Very old CMOS chips won't have settings for 1.44-MB or 2.88-MB 3.5-inch floppy disk drives because they were developed before these drives were introduced. Today the 5.25-inch drives are obsolete, and the CMOS of the future might not have settings for them. Several third-party utilities will allow the CMOS to accept the necessary values to support these drives. Errors Caused by the Floppy Disk If a floppy disk drive doesn't work, the first thing you should suspect is the floppy disk. To check a floppy disk, use the following procedure:

1. First, make sure the disk is not write protected. The hole on the right top corner of a 3.5-inch disk (viewed from the front) should be closed. On a 5.25-inch disk, the notch on one side should be visible (not covered).
2. Try another disk.
3. Try a new (formatted) disk.
4. Try someone else's disk—one that is known to work on another computer (first make sure there is no critical data on the disk).
5. If two or more disks are unreadable, the drive is suspect; try going to MS-DOS and reading a directory using the DIR command.

CAUTION

Never test a drive by using a disk that contains important data! If the drive is bad, it may destroy any disks placed into it.

Detecting Data Errors on a Disk

If you can read data from one disk, but not another, or if a disk is very slow reading or writing data, the problem is the floppy disk. Throw the offending disk away. Data errors on floppy disks generally result in an error message that ends with the words "Abort, Retry, Fail." The system will make 10 attempts to read data from a drive before reporting an error. If you get an error, it indicates that the disk is in pretty bad shape. Transfer the data as best you can to another drive, and discard the old disk. The process for repairing floppy disks is identical to the process for repairing hard disk drives, should there be data on the disk that must be recovered.

Check the CMOS Setting

Occasionally, the CMOS settings for floppy disks cause problems with drive operations. Any of the following errors indicates a possible CMOS setup problem:

• General failure reading drive A: (or B:)
• Not ready error reading drive A: (or B:)
• Insert disk for drive A: (or B:) and press any key when ready

BIOS makers often use the 3.5-inch high-density disk drive as the default CMOS setting for the A drive. With this BIOS, failure of the CMOS battery, or even accidental erasure of the CMOS, will still allow most floppy disks to work. Always double-check the CMOS if you are experiencing a recurrent floppy disk drive failure. It is quick, easy, and might save you time.

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It is possible for the CMOS to be corrupted by a software or hardware conflict and yet appear to be fine. If all else fails, reset the CMOS and reinstall the CMOS setup (check the motherboard manual for the jumper or disconnect the battery).

NOTE:

For more information and clarification with regard on this topics, feel free to read “A+ Certification Training Kit / Microsoft Corporation.--3rd Ed.” PUBLISHED BYMicrosoft PressA Division of Microsoft CorporationOne Microsoft WayRedmond, Washington 98052-6399 Copyright © 2001 by Microsoft Corporation