PECI Interface
74 Thermal/Mechanical Specifications and Design Guide
7.1.2.7.6 Package Temperature Read
This read returns the maximum processor die temperature in 16-bit PECI format. The
upper 16 bits of the response data are reserved.
7.1.2.7.7 Temperature Target Read
The Temperature Target Read allows the PECI host to access the maximum processor
junction temperature (T
jmax
) in degrees Celsius. This is also the default temperature
value at which the processor thermal control circuit activates. The T
jmax
value may vary
from processor part to part to reflect manufacturing process variations. The
Temperature Target read also returns the processor T
CONTROL
value. T
CONTROL
is
returned in standard PECI temperature format and represents the threshold
temperature used by the thermal management system for fan speed control.
7.1.2.7.8 Package Thermal Status Read / Clear
The Thermal Status Read provides information on package level thermal status. Data
includes:
• Thermal Control Circuit (TCC) activation
• Bidirectional PROCHOT_N signal assertion
•Critical Temperature
Both status and sticky log bits are managed in this status word. All sticky log bits are
set upon a rising edge of the associated status bit and the log bits are cleared only by
Thermal Status reads or a processor reset. A read of the Thermal Status word always
includes a log bit clear mask that allows the host to clear any or all of the log bits that
it is interested in tracking.
A bit set to ‘0’ in the log bit clear mask will result in clearing the associated log bit. If a
mask bit is set to ‘0’ and that bit is not a legal mask, a failing completion code will be
returned. A bit set to ‘1’ is ignored and results in no change to any sticky log bits. For
example, to clear the TCC Activation Log bit and retain all other log bits, the Thermal
Status Read should send a mask of 0xFFFFFFFD.
Figure 7-26. Package Temperature Read Data
PACKAGE_TEMPERATURE MSR
Sign
Bit
14
RESERVED
16
PECI Temperature
(Integer Value)
61531
PECI Temperature
(Fractional Value)
5 0
Figure 7-27. Temperature Target Read
TEMPERATURE_TARGET MSR
15
Processor Tjmax
16
T
CONTROL
823
RESERVED
7 0
RESERVED
31 24
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