Thermal Specifications
Figure 6-17. Thermal Data Configuration Register
3
1
4
3
0
Reserved
Thermal Filter Const
6.3.2.6.7
6.3.2.6.8
TCONTROL Read
TCONTROL is used for fan speed control management. The TCONTROL limit may be
read over PECI using this Mailbox function. Unlike the in-band MSR interface, this
TCONTROL value is already adjusted to be in the native PECI temperature format of a
2-byte, 2’s complement number.
T-state Throttling Control Read / Write
PECI offers the ability to enable and configure ACPI T-state (core clock modulation)
throttling. ACPI T-state throttling forces all CPU cores into duty cycle clock modulation
where the core toggles between C0 (clocks on) and C1 (clocks off) states at the
specified duty cycle. This throttling reduces CPU performance to the duty cycle
specified and, more importantly, results in processor power reduction.
The Intel Xeon Processor E7-8800/4800/2800 Product Families processor supports
software initiated T-state throttling and automatic T-state throttling as part of the
internal Thermal Monitor response mechanism (upon TCC activation). The PECI T-state
throttling control register read/write capability is managed only in the PECI domain. In-
band software may not manipulate or read the PECI T-state control setting. In the
event that multiple agents are requesting T-state throttling simultaneously, the CPU
always gives priority to the lowest power setting, or the numerically lowest duty cycle.
On Intel Xeon Processor E7-8800/4800/2800 Product Families processors, the only
supported duty cycle is 12.5% (12.5% clocks on, 87.5% clocks off). It is expected that
T-state throttling will be engaged only under emergency thermal or power conditions.
Future products may support more duty cycles, as defined in the following table:
Table 6-11. ACPI T-state Duty Cycle Definition
Duty Cycle Code
Definition
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
Undefined
12.5% clocks on / 87.5% clocks off
25% clocks on / 75% clocks off
37.5% clocks on / 62.5% clocks off
50% clocks on / 50% clocks off
62.5% clocks on / 37.5% clocks off
75% clocks on / 25% clocks off
87.5% clocks on / 12.5% clocks off
132
Datasheet Volume 1 of 2
INTEL [ INTEL ]
