Page 1:PC Diagnostics, Testing, And Maintenance
Page 2:The POST
Page 3:BIOS POST Beep Codes, Checkpoint Codes, And Onscreen Messages
Page 4:Peripheral And Operating System Diagnostics
Page 5:Commercial Diagnostics Software And Free/User Supported Diagnostics
Page 6:The Boot Process
Page 7:The Hardware Boot Process: Operating System Independent
Page 8:DOS And Windows 9x/Me Boot Processes And Windows 2000/XP Startup
Page 9:Windows 7/Vista And Windows 8 Startup
Page 10:PC Maintenance Tools
Page 11:Hand Tools Continued
Page 13:Test Equipment: Electrical, Loopback Connectors, And Meters
Page 14:Test Equipment: Logic Probes, Outlet Testers, And Memory Module Testers
Page 15:Special Tools For The Enthusiast
Page 16:Preventative Maintenance
Page 17:Cleaning A System
Page 18:System Disassembly And Cleaning Procedures
Page 19:Passive Preventive Maintenance Procedures
Page 20:Passive Preventive Maintenance Procedures Continued
Page 21:Troubleshooting Tips And Techniques
Page 22:Troubleshooting: Replacing Parts And The Bootstrap Approach
Page 23:Problems During POST, Running Software, And Adapter Cards
When IBM began shipping the original PC in 1981, it included safety features that had never been seen in a personal computer. These features were the POST and parity-checked memory. Although parity-checked or even error-correcting code (ECC) memory is no longer available in most non-server chipsets, every PC still executes a POST when you turn it on. The following sections provide more detail on the POST, a series of program routines buried in the motherboard ROM-BIOS chip that tests all the main system components at power-on time. This series of routines is partially responsible for the delay when you turn on your PC; the computer executes the POST before loading the operating system.
These tests check the primary components in your system, such as the CPU, ROM, motherboard support circuitry, memory, and major peripherals such as the expansion chassis. These tests are brief and are designed to catch hard (not intermittent) errors. The POST procedures are not very thorough compared to available disk-based diagnostics. The POST process provides error or warning messages whenever it encounters a faulty component.
Although the diagnostics performed by the system POST are not thorough, they are the first line of defense, especially when it comes to detecting severe motherboard problems. If the POST encounters a problem severe enough to keep the system from operating properly, it halts the system boot process and generates an error message that often identifies the cause of the problem. These POST-detected problems are sometimes called fatal errors because they prevent the system from booting.
Systems that use UEFI firmware also perform diagnostics tests, but depending upon the specific firmware in use, error messages may be stored in event logs, and beep codes may be used for some errors.
How Errors Are Displayed
The POST tests normally provide three types of output messages: audio codes, onscreen text messages, and hexadecimal numeric codes that are sent to an I/O port address.
POST errors can be displayed in the following three ways:
- Beep codes—Heard through the speaker or beeper attached to the motherboard. Note that some systems do not include a speaker.
- POST checkpoint codes—Hexadecimal checkpoint codes sent to an I/O port address. A special card plugged into an available expansion slot is required to view these codes.
- Onscreen messages—Error messages displayed onscreen after the video adapter is initialized.
Systems that use UEFI firmware might use beep and checkpoint codes but also store error messages in event logs.
- PC Diagnostics, Testing, And Maintenance
- The POST
- BIOS POST Beep Codes, Checkpoint Codes, And Onscreen Messages
- Peripheral And Operating System Diagnostics
- Commercial Diagnostics Software And Free/User Supported Diagnostics
- The Boot Process
- The Hardware Boot Process: Operating System Independent
- DOS And Windows 9x/Me Boot Processes And Windows 2000/XP Startup
- Windows 7/Vista And Windows 8 Startup
- PC Maintenance Tools
- Hand Tools Continued
- Test Equipment: Electrical, Loopback Connectors, And Meters
- Test Equipment: Logic Probes, Outlet Testers, And Memory Module Testers
- Special Tools For The Enthusiast
- Preventative Maintenance
- Cleaning A System
- System Disassembly And Cleaning Procedures
- Passive Preventive Maintenance Procedures
- Passive Preventive Maintenance Procedures Continued
- Troubleshooting Tips And Techniques
- Troubleshooting: Replacing Parts And The Bootstrap Approach
- Problems During POST, Running Software, And Adapter Cards