PECI Interface
64 Thermal/Mechanical Specifications and Design Guide
7.1.2.6.2 DRAM Thermal Estimation Configuration Data Read/Write
This feature is relevant only when activity-based DRAM temperature estimation
methods are being utilized and would apply to all the DIMMs on all the memory
channels. The write allows the PECI host to configure the ‘β’ and ‘θ’ variables in
Figure 7-10 for DRAM channel temperature filtering as per the equation below:
T
N
= β ∗ T
N-1
+ θ ∗ ΔEnergy
T
N
and T
N-1
are the current and previous DRAM temperature estimates respectively in
degrees Celsius, ‘β’ is the DRAM temperature decay factor, ‘ΔEnergy’ is the energy
difference between the current and previous memory transactions as determined by
the processor power control unit and ‘θ’ is the DRAM energy-to-temperature translation
coefficient. The default value of ‘β’ is 0x3FF. ‘θ’ is defined by the equation:
θ = (1 - β) ∗ (Thermal Resistance) ∗ (Scaling Factor)
The ‘Thermal Resistance’ serves as a multiplier for translation of DRAM energy changes
to corresponding temperature changes and may be derived from actual platform
characterization data. The ‘Scaling Factor’ is used to convert memory transaction
information to energy units in Joules and can be derived from system/memory
configuration information.
7.1.2.6.3 DRAM Rank Temperature Write
This feature allows the PECI host to program the temperature for all the ranks within a
DIMM up to a maximum of four ranks as shown in Figure 7-11. The DIMM index and
Channel inde x are specified through the parameter field as shown in Tab le 7 - 7 . This
write is relevant in platforms that do not have on-die or on-board DIMM thermal
sensors to provide memory temperature information or if the processor does not have
direct access to the DIMM thermal sensors.
Figure 7-10. DRAM Thermal Estimation Configuration Data
Memory Thermal Estimation Configuration Data
RESERVED
1031
BETA VARIABLE
9 0
THETA VARIABLE
1920
Table 7-7. Channel & DIMM Index decoding
Index Encoding Physical Channel# Physical DIMM#
000 0 0
001 1 Reserved
010 2 Reserved
011 3 Reserved
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