Chapter 20: Storage Devices and Interfaces

In Chapter 17 we discussed RAM, which is temporary or primary storage. In this chapter, we discuss forms of permanent or secondary storage devices, such as hard drives, floppy drives, Zip drives, tape devices, and optical storage. Permanent storage devices are sometimes referred to as mass storage or auxiliary storage devices. We also explore the interfaces and technologies used to connect storage devices to a computing system. Some of the more common interfaces are IDE/ATA, serial ATA and SCSI.

The core exam is likely to test your knowledge of the proper methods of configuring, connecting, and troubleshooting storage. It seems that the recent A+ Core Hardware exam focused heavily on storage devices. The current test will probably concentrate on your ability to install and configure multiple hard drives, and dwell on the details of SCSI configurations and priorities. Pay close attention to the topics discussed in this chapter; they may make the difference on whether you pass or fail the core exam.

THE FLOPPY DRIVE

A floppy drive is an internal device that reads or writes information to and from magnetic floppy disks, and communicates with the system’s CPU. The floppy drive is typically mounted into an available drive bay inside the system unit. A floppy drive adapter kit may be necessary if you are installing a floppy drive unit into a large drive bay. Older computing systems used 5.25-inch floppy drives that required a larger bay. Today, most computing systems come with a standard 3.5-inch floppy drive installed. Similar to a hard drive, a floppy disk stores information on magnetic media. A hard drive’s storage medium is called a platter. A floppy drive’s storage medium is called a floppy disk. The major advantage of a floppy disk is that it is portable. You can store files on a floppy disk and take it wherever you go. The major disadvantages of floppy disks are that they are slow to access and cannot store as much information as a hard disk.

A floppy disk must receive both a low-level format and a high-level format before it can be considered useful.

A low-level format prepares the floppy disk with an organized structure by creating sectors, tracks, and clusters on the floppy disk. A high-level format prepares the floppy disk with a File Allocation Table (FAT) and adds a root directory to it. You can format a floppy from a DOS command prompt or through the use of an operating system GUI, such as Windows. Preformatted floppy disks can be purchased just about anywhere computer supplies are sold.

To format a floppy disk from a DOS prompt, simply place the disk in the floppy drive “A” and type “format a:”. A low-level format as well as a high-level format will be carried out on the disk. When the format process is complete, the floppy will be ready to have files saved to it. (See the section “The Hard Drive” later in this chapter for more information on the formatting process.)

There are two basic forms of floppy disk media available:

5.25-inch: This style of floppy disk was popular in the1980s. The 5.25-inch floppy came with two common data storage capacities: 360K and 1.2MB. The 5.25-inch floppy disk used a 5.25-inch floppy drive that is now considered obsolete.

3.5-inch: This floppy drive is found in most computers today. The 3.5-inch floppy disk can store 720K (double density) or 1.44MB (high density) of data.

Floppy Drive Components

A floppy drive’s components are similar to that of a hard drive. The basic components that make up floppy drives include the read/write heads, which read and write data onto the floppy media and work in tandem with an erase tunnel mechanism to erase information if requested by the floppy drive’s controller. The head actuator, sometimes referred to as a stepping motor, is controlled by the floppy disk controller; it moves the drive’s read/write heads in and out of place. A spindle motor, driven by a belt system, makes the floppy disk spin or rotate at the desired speed. The speed at which the floppy disk spins is measured in revolutions per minute. A floppy drive uses a circuit board, also known as a logic board, which controls all of the floppy drive’s components and communicates with the computer system. Finally, there are two floppy drive connectors. One is used to connect the floppy drive to the system’s power supply, and the other is used to connect the floppy drive to the motherboard’s floppy drive controller.

Floppy Drive Configuration and Troubleshooting

A floppy drive is connected to a floppy drive controller on the motherboard with a data cable. The data cable has a red stripe that runs down its right side. The red stripe represents pin 1 on the data cable. When plugging the data cable connector into the floppy drive controller on the motherboard, you must match pin 1 on the data cable connector to pin 1 on the controller. The same is true when connecting the other end of the data cable to the floppy drive itself. If you plug the floppy drive’s data cable in backward, the LED light on the front of the floppy drive unit will stay lit, and you will not be able to access the floppy drive.

A computer system reserves certain letter designations for its components. The primary hard drive gets the letter designation of C by default. The letters A and B are reserved by the system for assignment to the floppy drives. A typical 3.5-inch floppy drive is attached to the far end of a ribbon data cable (after the twist in the ribbon cable) and gets the letter A assignment. If you have a second floppy drive, such as a 5.25-inch floppy drive, it should be attached to the middle connector on the floppy data cable, and it gets the letter B assignment.

Over time, floppy drives and floppy disks can get dirty and warped. This can cause them to fail mechanically or render them incapable of data storage and retrieval. If you attempt to access your floppy drive and receive an error message such as “Drive A is not ready, Abort, Retry or Fail,” either your floppy disk is bad or your floppy drive needs cleaning and/or maintenance.

There are times when you may need to boot up your computer with a bootable floppy disk installed in the A drive. This is frequently done for troubleshooting purposes, maintenance, or operating system installation. If you are unable to boot from your bootable floppy disk, check your boot sequence settings in the BIOS configuration and verify that your system is set to boot from the A drive before the C or D drive. Otherwise, the system will not look for your bootable floppy at start-up.

One of the most common mistakes people make is to leave a nonbootable floppy disk in a floppy drive when restarting the system. This can cause the error message “Nonsystem disk or disk error; replace and strike any key to continue.” Ejecting the nonbootable floppy from the drive and pressing any key on your keyboard will bypass this error message, and your system will continue to load. (By the way, there is no such thing as an “any” key.)

Exchanging floppy disks with others and using them in your system without proper virus protection poses a serious virus threat to your computer. The two most common sources of virus attack come from floppy disks and the Internet. Always scan your floppy media for viruses.