Datasheet

Interfaces
Intel
®
Xeon
®
Processor C5500/C3500 Series
Datasheet, Volume 1 February 2010
62 Order Number: 323103-001
2.1.14.5.2 Virtual Temperature Sensor
The weights of the commands and the cooling coefficient can be dynamically modified
by fan control firmware to update the virtual temperature according to current airspeed
and ambient temperature. Care must be taken to avoid invalidating the virtual
temperature. For example, when fan speeds are increased, the cooling coefficient
should not be increased until the airspeed at the DIMM is sure to have reached the
steady state value associated with the fan speed command. It is acceptable to reduce
the cooling coefficient immediately on a fan speed decrease.
The thermal throttling logic implements this equation every DCLK:
T(t+1) = T(t) * (1 - c*2-36) + w*2-37
where:
T is virtual temperature
t is time
c is cooling coefficient
w is the weight of the command executed in cycle t
Figure 11. Mapping Throttlers to Ranks
Channel 2
Duty Cycle
EXTTS
(Some DIMM Hot)
MinThrottle
DutyCycle
256 Off M On
Meta-
stability
Virtual Temp
Sensor 0
Ch0ThrottleRank[7:0]
Rank Mapping
Duty Cycle
Duty Cycle
Duty Cycle
Channel 0
Channel 1
Ch1ThrottleRank[7:0]
Ch2ThrottleRank[7:0]
Throttle
Now
Virtual Temp
Sensor 1
Throttle
Now
Virtual Temp
Sensor 2
Throttle
Now
Virtual Temp
Sensor 3
Throttle
Now
Throttle
Mode