HP Compaq d330 DT User Manual

Chapter 4 System Support
4.7.4 THERMAL SENSING AND COOLING
All systems feature a variable-speed fan mounted as part of the processor heatsink assembly.
Desktop and Configurable Minitower systems provide an auxiliary chassis fan. All fans are
controlled through temperature sensing logic on the system board and/or in the power supply.
There are some electrical differences between form factors and between some models, although
the overall functionally is the same. 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).
Figure 4-12 shows the fan control circuitry for desktops and minitower units. The RPM (speed)
of all fans is the result of the temperature of the CPU as sensed by the Control ASIC and indicated
to the Speed Control circuitry. The fans are controlled by circuitry to run at the slowest (quietest)
speed that will maintain proper cooling. NOTE: Units using chassis and CPU fans must have
both fans connected to their corresponding headers to ensure proper cooling of the system.
+12 VDC
Figure 4-12. Fan Control Block Diagram
CH Fan
Processor
OVR RD
(-)
(+)
3
2
as Fan
a P8
1
Ch sis
derHe
Sense
Fan
CH
(-)
(+)
3
2
CPU Fan
e r
P70
1
H ade
CPU
Fan
Sense
2
P16
1
PWR
CPU
Fan
Control
Speed
Control
PWR
CH
Fan
Control
I/O
Controller
Fan S
p
eed
Control
ASIC
CH Fan Sense
ICH5
CPU Fan Sense
Fan Sns
Fan Clamp
PS Fan
Sense
PS Fan Sense
Fan CMD
Power
Supply
Assembly
hp compaq d330 and d530 Series of Personal Computers
Featuring the Intel Pentium 4 Processor
First Edition – June 2003
4-28

HP Compaq d330 DT Specifications

General

Brand	HP
Model	Compaq d330 DT
Category	Desktop
Language	English