POST Power-On Sequence

When a Compaq Personal Computer or workstation is turned on, the computer reads its first instructions from memory. It finds the instructions from the power-on restart vector addressed in ROM and begins executing those instructions. The instructions begin with a series of ROM- resident diagnostic tests called the Power-On Self-Test (POST) to determine if the computer is operational and ready to accept an operating system. The normal checking procedure for POST includes:

1.BIOS memory is tested and initialized (the first 128K of RAM is not displayed). If the system does not pass the first memory check, an immediate error message is displayed and the initialization process stops. The cause of a failure at this stage might be a problem with the ROM, the system board, the CPU, or memory.

2.The system board and bus devices are quick-tested to determine if the interrupt controllers, DMA controllers, keyboard controller, video display controller, interval timers, diskette drive controller, serial and parallel port controller, and fixed disk controller are all properly installed and are functioning properly.

3.The remaining memory is tested and the count displayed on the monitor only when starting the machine from the off mode. You should verify that the memory displayed corresponds with the memory installed in the computer.

4.The keyboard, drives, and their controllers are initialized and tested. Test results are shown via the LEDs on the keyboard and computer case.

5.CMOS memory is checked for configuration, time, and date. If the CMOS memory parameters do not match the actual system configuration, a "162-System Options" error or a “System CMOS” error will be displayed with instructions for restarting the computer.

6.The speaker will sound two short beeps or will display the Compaq splash screen when the POST has been successfully completed. Refer to the POST error messages when error messages are displayed on the screen or when beep patterns are sounded.

Compaq Drive Protection System

The Compaq Drive Protection System (DPS) is a diagnostic tool built into the hard drives installed in select Compaq Deskpro computers and workstations. DPS is designed to help diagnose problems that might result in unwarranted hard drive replacement.

When Compaq Deskpro Computers and workstations are built, each installed hard drive is tested using DPS and a permanent record of key information is written onto the drive. Each time DPS is run, test results are written to the hard drive. This information may be used to help diagnose the hard drive and the computer system.

Running DPS will not affect any programs or data stored on the hard drive. The test resides in the hard drive firmware and can be executed even if the computer will not boot to an operating system. The time required to execute the test depends on the manufacturer and size of the hard drive; in most cases, the test will take approximately 2 minutes per gigabyte.

DPS should be used when you suspect a hard drive problem. If the computer reports a SMART Hard Drive Detect Imminent Failure message, there is no need to run DPS; instead, back up the information on the hard drive and replace the hard drive.

Quick Troubleshooting Guide

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