Compaq W4000 manual Small Form Factor Fan Control Block Diagram

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 and the Therm- 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

ASIC

		Fan Header
	Speed	(-)	P70
			1
	Control	+5 VDC (+)
			2
			3
Fan		P1	Fan
Sense		10	Sink
			Fan
Fan CMD
		13	SPD
Therm-
Interrupt	82801
SMBus	ICH2

Power Supply Assembly

PS Fan

Speed(-)

Control

+5 VDC (+)

PS

Circuits

Figure 4-11.Small Form Factor Fan Control Block Diagram

Processor

Control

ASIC

		Chassis Fan		CPU Fan Header
		Header P8				P70
		(-)	1		(-)	1
		+5 VDC (+)		+5 VDC	(+)
			2			2
			3			3
Chassis
Fan Sense		P1	Fan	Power Supply Assembly
CPU Fan Sense		24	Sink
			Fan			PS Fan
Fan CMD				Speed
		12	SPD			(-)
				Control
Therm-						+5 VDC (+)
	82801
SMBus
	ICH2			PS
				Circuits

Figure 4-12.Desktop/Configurable Minitower Fan Control Block Diagram

4-30Compaq Evo and Workstation Personal Computers

Featuring the Intel Pentium 4 Processor

Second Edition – January 2003