Guide

Thermal and Mechanical Design
Intel® Xeon® Processor E7 2800/4800/8800 v2 Product Family 43
Thermal/ Mechanical Specifications and Design Guide
T
DTS
= T
LA
+ Ψ
pa
* P * F
Where T
LA
and Ψ
pa
are the intercept and slope terms from the T
DTS
equations. To
implement the DTS based thermal specification, these equations must be programmed
in firmware. Since the equations differ with processor SKU, SKUs can be identified by
TDP and Core Count. The following PECI commands can be used to read TDP and Core
Count from the processors:
TDP: RdPkgConfig(), Package Power SKU [LOW] Read, 14:0
Core Count: RdPCIConfigLocal()
Power (P) is calculated in Section 2.2.3.2.2. As power dynamically changes, the
specification also changes, so power and T
DTS
calculations are recommended every 1
second.
Correction factor (F) compensates for the error in power monitoring. The current
estimate for F is 0.95.
The Tcontrol
portion of the DTS based thermal specification is a one time calculation:
T
control_spec
= T
LA
+ Ψ
pa
* TDP - Tcontrol + Tcontrol_offset
Tcontrol is defined in Section 2.3.2.Tcontrol_offset is defined in Section 2.3.3
The final DTS based thermal specification is the maximum of both:
T
DTS_max
= max[T
control_spec
, T
DTS
]
The margin (M) between the actual die temperature and the DTS based thermal
specification is used in the fan speed control algorithm. When M < 0, increase fan
speed. When M > 0, fan speed may decrease.
M = T
DTS_max
- Tsensor
OR
M = T
DTS_ave
– Tsensor
Tsensor represents the absolute temperature of the processor as power changes:
Tsensor = TEMPERATURE_TARGET + DTS
T
DTS_ave
is defined in Section 2.2.3.2.3.
TEMPERATURE_TARGET, the temperature at which the processor thermal control circuit
activates, is a one time PECI readout: RdPkgConfig(), Temperature Target Read, 23:16.
DTS, the relative temperature from thermal control circuit activation, is negative by
definition, and changes instantaneously. DTS command info is given in Section 2.3.2.
2.2.3.2.2 Power Calculation
To implement DTS based thermal specification, average power over time must be
calculated:
P = (E2 - E1) / (t2 - t1)
Where:
t1 = time stamp 1
t2 = time stamp 2
E1 = Energy readout at time t1
E2 = Energy readout at time t2