Compaq W4000 Technical Reference Manual page 84

Chapter 4 System Support
High and low thermal parameters are programmed into the ASIC by BIOS during POST. If the
high thermal parameter is reached then the fan(s) will be turned on full speed
signal will be asserted. The asserted Therm- signal can, with the proper software setup, be used by
the 82801 ICH2 to initiate an AOL message for transmission over a network (refer to Network
Interface Controller subsection in Chapter 5).
NOTE: These systems do not support thermister-based fans used on earlier products.
Processor
Control
ASI C
F igure 4-11. Sm ll Form Factor Fan
Processor
Cont rol
AS IC
Figure 4 -12. Desktop/Configurable Minitower Fan Control Block D
Compaq Evo and Workstation Personal Computers
4-30
Featuring the Intel Pentium 4 Processor
Speed
Control
Fan
Sense
Fan CMD
Therm-
Interrupt
82801
ICH2
SMBus
a Control Block Diagram
Chassis
Fan Sense
CPU Fan Sense
Fan CMD
Therm-
82 801
SMBus
ICH2
Second Edition – January 2003
Fan Header
P70
(-)
1
+5 VDC (+)
2
3
P1
Fan
Power Supply Assembly
Sink
10
Fan
SPD Speed
13
Control
Circuits
Chassis Fan
Header P8
(-)
1
(+)
+5 VDC
2
3
Fan
P1
Sink
24
Fan
SPD
12
iagram
and the Therm-
PS Fan
(-)
(+)
+5 VDC
PS
CPU Fan Header
P70
(-)
1
(+)
+5 VDC
2
3
Power Supply Assembly
PS Fan
Speed
(-)
Control
(+)
+5 VDC
PS
Circuits