w83795g Winbond Electronics Corp America, w83795g Datasheet - Page 118

• Manufacturer Part Number: w83795g
• Description: Nuvoton H/w Monitor
• Manufacturer: Winbond Electronics Corp America

W83795G/ADG
11. PECI CONTROL AND SB-TSI FUNCTION
11.1
PECI Control Registers
Intel® new generation CPUs such as Presler begin to support new single wire digital temperature
monitoring interface which is called Platform Environment Control Interface or PECI. The
W83795G/ADG supports the PECI* version 2.0 for these new generation CPUs. All PECI control
registers are located in Bank 3.
The W83795G/ADG PECI configuration, including the PECI address and number of domains, must
match the CPU type. BIOS have to detect which kind of CPU it is and program the correct configuration
in the W83795G/ADG.
PECI (Platform Environment Control Interface) is a new digital interface to read the CPU temperature of
Intel® CPUs. With a bandwidth ranging from 2 Kbps to 2 Mbps, PECI uses a single wire for
self-clocking and data transfer. By interfacing to the Digital Thermal Sensor (DTS) in the Intel® CPU,
PECI reports a negative temperature (in counts) relative to the processor’s temperature at which the
thermal control circuit (TCC) is activated. At the TCC Activation temperature, the Intel CPU will operate
at reduced performance to prevent the device from thermal damage.
PECI is one of the temperature sensing methods that the W83795G/ADG supports. The
W83795G/ADG contains a PECI master and reads the CPU PECI temperature. The CPU is a PECI
client.
The PECI temperature values returning from the CPU are in “counts” which are approximately linear in
relation to changes in temperature in degrees centigrade. However, this linearity is approximate and
cannot be guaranteed over the entire range of PECI temperatures. For further information, refer to the
PECI specification. All references to “temperature” in this section are in “counts” instead of “°C”.
Figure-1 shows a typical fan speed (PWM duty cycle) and PECI temperature relationship.
Figure-1 PECI Temperature
- 118 –
Aug/2/2010
Revision 1.41