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A+ Exam Cram: Hardware Troubleshooting Techniques

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Sometimes, it can be difficult to determine whether the cause of a problem lies in the hardware or the software. This sample chapter will help you to make this determination to make fixing problems even easier.
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Sorting Hardware/Software/Configuration Problems

One of the first steps in troubleshooting a computer problem (or any other programmable system problem) is to determine whether the problem is due to a hardware failure or to faulty software. In most PCs, you can use a significant event that occurs during the startup process as a key to separate hardware problems from software problems: the single beep that most PCs produce between the end of the power-on self test (POST) and the beginning of the startup process.

Errors that occur, or are displayed, before this beep indicate that a hardware problem of some type exists. Up to this point in the operation of the system, only the BIOS and the basic system hardware have been active. The operating system side of the system does not come into play until after the beep occurs.

If the system produces an error message (such as "The system has detected unstable RAM at location x") or a beep code before the single beep occurs, the system has found a problem with the hardware. In this case, a bad RAM memory device is indicated.

Typically, if the startup process reaches the point at which the system's CMOS configuration information is displayed onscreen, you can safely assume that no hardware configuration conflicts exist in the system's basic components. After this point in the bootup process, the system begins loading drivers for optional devices and additional memory.

If the error occurs after the CMOS screen displays and before the bootup tone, you must clean boot the system and single-step through the remainder of the bootup sequence.

You can still group errors that occur before the beep into two distinct categories:

  • Configuration errors

  • Hardware failures

A special category of problems tends to occur when a new hardware option is added to the system, or when the system is used for the very first time. These problems are called configuration problems, or setup problems. These problems result from mismatches between the system's programmed configuration held in CMOS memory and the actual equipment installed in the system.

It is usually necessary to access the system's CMOS setup utility in the following three situations:

  • When the system is first constructed.

  • When it becomes necessary to replace the CMOS backup battery on the system board.

  • When a new or different option is added to the system (such as memory devices, hard drives, floppy drives, or video display), it might be necessary to access the setup utility to accept the changes that have been implemented.

In most systems, the BIOS and operating system use plug-and-play techniques to detect new hardware that has been installed in the system. These components work together with the device to allocate system resources for the device. In some situations, the PnP logic is not able to resolve all the system's resource needs and a configuration error occurs. In these cases, the user must manually resolve the configuration problem.

When you are installing new hardware or software options, be aware of the possibility of configuration errors occurring. If you encounter configuration (or setup) errors, refer to the installation instructions found in the new component's installation/user documentation.

If you cannot confirm a configuration problem, you most likely have a defective component. The most widely used repair method involves substituting known-good components for suspected bad components. Other alternatives for isolating and correcting a hardware failure that appears before the bootup depend on how much of the system is operable.

Normally, symptoms can be divided into three sections: configuration problems, bootup problems, and operational problems.

The system's configuration settings are normally checked first. It is important to observe the system's symptoms to determine in which part of the system's operation the fault occurs. The error messages described in Table 3.1 are errors that occur and are reported before the single beep tone is produced at the end of the POST routines.

Table 3.1 Common Configuration Error Codes

After the beep tone has been produced in the startup sequence, the system shifts over to the process of booting up and begins looking for and loading the operating system. Errors that occur between the beep and the presentation of the operating system's user interface (command prompt or GUI) generally have three possible sources. These sources are summarized in the following list that includes the typical error messages associated with each source.

  • Hardware failure (physical problem with the boot drive)

  • General Failure Error Reading Drive x

  • Corrupted or missing boot files

  • Bad or Missing Command Interpreter

  • Nonsystem Disk or Disk Error

  • Bad File Allocation Table

  • Corrupted or missing operating system files

Both configuration problems and bootup problems can be caused by a hardware or operational failure. If the configuration settings are correct, but these symptoms are present, a hardware problem is indicated as the cause of the problem. Conversely, bootup problems are typically associated with the operating system.

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