Intel QX9775 EU80574XL088N データシート
製品コード
EU80574XL088N
Datasheet
83
Thermal Specifications
5.3.1.1
T
CONTROL
and TCC Activation on PECI-based Systems
Fan speed control solutions based on PECI utilize a T
CONTROL
value stored in the
processor IA32_TEMPERATURE_TARGET MSR. The T
CONTROL
MSR uses the same offset
temperature format as PECI though it contains no sign bit. Thermal management
devices should infer the T
CONTROL
value as negative. Thermal management algorithms
should use the relative temperature value delivered over PECI in conjunction with the
T
CONTROL
MSR value to control or optimize fan speeds.
shows a conceptual
fan control diagram using PECI temperatures.
The relative temperature value reported over PECI represents the data below the onset
of thermal control circuit (TCC) activation as needed by PROCHOT# assertions. As the
temperature approaches TCC activation, the PECI value approaches zero. TCC activates
at a PECI count of zero.
5.3.1.2
Processor Thermal Data Sample Rate and Filtering
The Digital Thermal Sensor (DTS) provides an improved capability to monitor device
hot spots, which inherently leads to more varying temperature readings over short time
intervals. The DTS sample interval range can be modified, and a data filtering algorithm
can be activated to help moderate this. The DTS sample interval range is 82 us
(default) to 20 ms (max). This value can be set in BIOS.
To reduce the sample rate requirements on PECI and improve thermal data stability vs.
time the processor DTS also implements an averaging algorithm that filters the
incoming data. This is an alpha-beta filter with coefficients of 0.5, and is expressed
mathematically as: Current_filtered_temp = (Previous_filtered_temp / 2) +
(new_sensor_temp / 2). This filtering algorithm is fixed and cannot be changed. It is on
by default and can be turned off in BIOS.
Host controllers should use the min/max sample times to determine the appropriate
sample rate based on the controller's fan control algorithm and targeted response rate.
The key items to take into account when settling on a fan control algorithm are the DTS
sample rate, whether the temperature filter is enabled, how often the PECI host will
poll the processor for temperature data, and the rate at which fan speed is changed.
Depending on the designer’s specific requirements the DTS sample rate and alpha-beta
filter may have no effect on the fan control algorithm.
Figure 5-5. Conceptual Fan Control Diagram of PECI-based Platforms
Fan Speed
(RPM
)
(not intended to depict actual im
plem
entation)
M
ax
M
in
Tem
perature
PECI = -10
PECI = -20
TCC A
ctivation
Tem
perature
T
CO
NTRO
L
Setting
PECI = 0
Fan Speed
(RPM
)
(not intended to depict actual im
plem
entation)
M
ax
M
in
Tem
perature
PECI = -10
PECI = -20
TCC A
ctivation
Tem
perature
T
CO
NTRO
L
Setting
PECI = 0