Thin Mini-ITX Internal Electrical Interfaces
Thin Mini-ITX Based PC System Design Guide 31
2.8 Fans
Chassis that have only one fan must have the fan plugged into the CPU specific header
on the motherboard. For systems that have two fans, the CPU cooling fan is to be
plugged into the CPU fan header, and the second fan is to be plugged into the system
fan header.
Motherboards should support both CPU and System fan headers so they may be used
in systems that require two blowers/fans. Atom based boards only need to support a
single fan header.
4-pin/wire fans and headers shall follow the 4-Wire Pulse Width Modulation (PWM)
Controlled Fans Specification.
2.8.1 CPU Fan
Boards must implement a 4-pin fan header for a CPU heatsink 4-wire fan. CPU fan
header must be colored white.
CPU fan header: 2A continuous current draw
Figure 2-15. 4-Pin CPU Fan Header
2.8.2 System Fan
A PWM controlled, 4-pin/wire system fan design must be implemented on
boards/chassis used in All-In-One PC’s. Tiny PC’s are to implement a 3-pin/wire
system fan design that is linearly/voltage controlled. In either situation, the system
fan header on the motherboard and the mating connector of the fan must be a color
other than white to separate it from the CPU fan header.
The motherboard ODM is responsible for providing a mechanism to enable the end
user to specify the applicable implementation. The motherboard design must default
to a 3-pin/wire implementation
System fan header: 1.5A continuous current draw
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