Technical Reference Guide

Table 4-16.System Operational Status LED Indications

Table 4-16.

System Operational Status LED Indications

 

Power

Hard Drive

System Status

LED

LED

S0: System on (normal operation)

Steady green

Green w/HD activity

S1: Suspend

Blinks green @ 1 Hz

Off

S3: Suspend to RAM

Blinks green @ 1 Hz

Off

S4: Suspend to disk

Blinks green @ 0.5 Hz

Off

S5: Soft off

Off - clear

Off

Processor not seated

Steady red

Off

CPU thermal shutdown

Off (system powers down)

Off (system powers down)

ROM error

Blinks red @ 1 Hz

Off

Power supply crowbar activated

Blinks red @ .5 Hz

Off

System off

Off

Off

4.7.4 THERMAL SENSING AND COOLING

All systems feature a variable-speed fan as part of the power supply assembly. All systems also provide a system board connection for a processor fan, which is present in all units. Desktop and Configurable Minitower systems provide an auxiliary chassis fan. All fans are controlled through temperature sensing logic both on the system board and in the power supply. Electrically, there are slight differences between the Small Form Factor (Figure 4-11) and the desktop and configurable minitower (Figure 4-12), although functionally operation is the same.

An ASIC monitors a thermal diode internal to the processor and provides a Fan CMD signal that the Speed Control logic uses to vary the speed of the fan(s) through the negative terminal of the fan(s). The turning off of the fan(s) as the result from the system being placed into a Sleep condition is initiated by the control ASIC asserting the Fan Off- signal, which results in the On/Off Control logic shutting off the +12 volts to the fan(s).

The main differences between the system types are as follows:

In the Small Form Factor system the processor fan, controlled by a separate speed control circuit, is mounted in the front of the chassis (separate from the heat sink assembly) and air is conducted across the processor's heat sink by an air baffle.

Desktop/Configurable Minitower systems use an integrated heat sink/fan assembly, with all fans speed-controlled by the ASIC through the power supply so that a thermal condition of the processor or power supply will affect all fans simultaneously.

Typical cooling conditions include the following:

1.Normal – Low fan speed.

2.Hot processor – ASIC directs Speed Control logic to increase speed of fan(s).

3.Hot power supply – Power supply increases speed of fan(s).

4.Sleep state – Fan(s) turned off. Hot processor or power supply will result in starting fan(s).

Compaq Evo and Workstation Personal Computers4-29

Featuring the Intel Pentium 4 Processor

Second Edition - January 2003

Page 83
Image 83
Compaq W4000 manual Thermal Sensing and Cooling, System Operational Status LED Indications, Power Hard Drive System Status