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Power-on sequence

At power-on, the ash boot block code initializes the hardware to a known state, then performs basic power-

on diagnostic tests to determine the integrity of the hardware. Initialization performs the following functions:

1. Initializes CPU and memory controller.

2. Initializes and congures all PCI devices.

3. Initializes VGA software.

4. Initializes the video to a known state.

5. Initializes USB devices to a known state.

6. Performs power-on diagnostics. For more information, see “Power-On Diagnostic Tests”.

7. The unit boots the operating system.

Power-on diagnostic tests

The Power-on diagnostics performs basic integrity tests of the hardware to determine its functionality and

conguration. If a diagnostic test fails during hardware initialization the unit simply stops. There are no

messages sent to video.

NOTE: You may try to restart the unit and run through the diagnostic tests a second time to conrm the rst

shutdown.

The following table lists the tests that are performed on the unit.

Test Description

Boot Block Checksum Tests boot block code for proper checksum value

DRAM Simple write/read pattern test of the rst 640k of memory

Serial Port Tests the serial port using simple port verication test to determine if ports are present

Timer Tests timer interrupt by using polling method

RTC CMOS battery Tests integrity of RTC CMOS battery

NAND ash device Tests for proper NAND ash device ID present

Troubleshooting

Basic troubleshooting

If the computer is experiencing operating problems or will not power on, review the following items.

Issue

Procedures

The computer unit is experiencing operating

problems.

Ensure that the following connectors are securely plugged into the computer:

Power connector, keyboard, mouse, network RJ-45 connector, monitor

The computer does not power on. 1. Verify that the power supply is good by installing it on a known working unit

and testing it. If the power supply does not work on the test unit, replace the

power supply.

66 Chapter 10 Diagnostics and troubleshooting

HP mt42 User Manual

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