Thermal/Mechanical Specifications and Design Guide 65
PECI Interface
7.1.2.6.4 DIMM Temperature Read
This feature allows the PECI host to read the temperature of all the DIMMs within a
channel up to a maximum of one DIMMs. This read is not limited to platforms using a
particular memory temperature source or temperature estimation method. For
platforms using DRAM thermal estimation, the PCU will provide the estimated
temperatures. Otherwise, the data represents the latest DIMM temperature provided
by the TSOD. Refer to Tab le 7 - 7 for channel index encodings.
7.1.2.6.5 DIMM Ambient Temperature Write / Read
This feature allows the PECI host to provide an ambient temperature reference to be
used by the processor for activity-based DRAM temperature estimation. This write is
used only when no DIMM temperature information is available from on-board or on-die
DIMM thermal sensors. It is also possible for the PECI host controller to read back the
DIMM ambient reference temperature.
Since the ambient temperature may vary over time within a system, it is recommended
that systems monitoring and updating the ambient temperature at a fast rate use the
‘maximum’ temperature value while those updating the ambient temperature at a slow
rate use an ‘average’ value. The ambient temperature assumes a single value for all
memory channel/DIMM locations and does not account for possible temperature
variations based on DIMM location.
Figure 7-11. DRAM Rank Temperature Write Data
15 7 0
Rank Temperature Data
Rank# 3
Absolute Temp
(in Degrees C)
Rank# 2
Absolute Temp
(in Degrees C)
Rank# 1
Absolute Temp
(in Degrees C)
Rank# 0
Absolute Temp
(in Degrees C)
816232431
15
2
Parameter format
Reserved DIMM Index
6
Channel Index
5 3 0
Figure 7-12. DIMM Temperature Read / Write
15 7 0
DIMM Temperature Data
Reserved Reserved
DIMM# 0
Absolute Temp
(in Degrees C)
816232431
15
2
Parameter format
Reserved Channel Index
3 0
Reserved
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