Thermal Specifications
Should a requested value be below Pn, it will be clamped at Pn. Should a requested
value be greater than P1, the value will be clipped to P1+1 for those Intel Xeon
Processor E7-8800/4800/2800 Product Families processors which support Intel Turbo
Boost Technology, and P1 for those which do not.
This setting is persistent across warm resets.
6.3.2.6.12
6.3.2.7
Read P-State Limit
This mailbox command is used by the PECI host to read out a socket's current sideband
P-state frequency ratio upper limit. If the value written is greater than allowed by the
ACPI table, the largest legal value will be returned. If the value written is lower than
allowed by the ACPI table, the lowest legal value will be returned. A value of P1+1
indicates enabling of all available P-states.
MbxSend()
The MbxSend() command is utilized for sending requests to the generic Mailbox
interface. Those requests are in turn serviced by the processor with some nominal
latency and the result is deposited in the mailbox for reading. MbxGet() is used to
retrieve the response and details are documented in Section 6.3.2.8.
The details of processor mailbox capabilities are described in Section 6.3.2.6.1, and
many of the fundamental concepts of Mailbox ownership, release, and management are
discussed in Section 6.3.2.9.
6.3.2.7.1
Write Data
Regardless of the function of the mailbox command, a request type modifier and 4-byte
data payload must be sent. For Mailbox commands where the 4-byte data field is not
applicable (for example, the command is a read), the data written should be all zeroes.
Figure 6-19. MbxSend() Command Data Format
0
1
2
3
4
Byte #
Byte
Definition
Request Type
Data[31:0]
Because a particular MbxSend() command may specify an update to potentially critical
registers inside the processor, it includes an Assured Write FCS (AW FCS) byte as part
of the write data payload. In the event that the AW FCS mismatches with the client-
calculated FCS, the client will abort the write and will always respond with a bad Write
FCS.
6.3.2.7.2
Command Format
The MbxSend() format is as follows:
Write Length: 7
Read Length: 1
Command: 0xd1
Multi-Domain Support: Yes (see Table 6-15)
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Datasheet Volume 1 of 2
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