W83627DHG-PT Nuvoton Technology Corporation of America, W83627DHG-PT Datasheet - Page 51

• Manufacturer Part Number: W83627DHG-PT
• Manufacturer: Nuvoton Technology Corporation of America

Specifications of W83627DHG-PT

• Pin Count: 128
• Lead Free Status / RoHS Status: Compliant

In this illustration, when PECI temperature is -20, the PWM duty cycle for fan control is at Duty2.
When CPU is getting hotter and the PECI temperature is -10, the PWM duty cycle is at Duty1.
At TControl PECI temperature, the recommendation from Intel is to operate the CPU fan at full speed.
Therefore Duty1 is 100% if this recommendation is followed. The value of TControl can be obtained by
reading the related Machine Specific Register (MSR) in the Intel CPU. The TControl MSR address is
usually in the BIOS Writer’s guide for the CPU family in question. Refer to the relevant CPU
documentation from Intel for more information. In this example, TControl is -10.
When the PECI temperature is below -20, the duty cycle is fixed at Duty2 to maintain a minimum (and
constant) RPM for the CPU fan.
W83627DHG-P’s fan control circuit can only accept positive real-time temperature inputs and limits
setting (in Smart Fan ™ mode). The device provides offset registers to ‘shift’ the negative PECI
readings to positive values otherwise the fan control circuit will not function properly. The offset
registers are the TBase registers located at Logical Device C, CR [E1h] ~ CR [E4h]. These registers
should be programmed with (positive) values so that the resultant value (Tbase + PECI) is always
positive. The unit of the TBase register contents is “count” to match that of PECI values. The resultant
value (TBase + PECI) should not be interpreted as the “temperature” (whether in count or °C) of the
PECI client (CPU).
Figure 8-9
Figure
Fan Speed
(PWM Duty Cycle)
8-8). This view is from the perspective of the W83627DHG-P fan control circuit.
Duty1
Duty2
shows the temperature/fan speed relationship after Tbase offsets are applied (based on
-20
Figure 8-8 PECI Temperature
PECI Temperature (counts)
W83627DHG-P/W83627DHG-PT
Tcontrol
-41-
-10
Publication Release Date: July 09, 2009
TCC Activation
0
Version 1.94