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Intel® Xeon® Processor E5-1600/E5-2600/E5-4600 Product Families 57
Datasheet Volume One
‘Power Limit 1’ values may be impacted by the processor heat sinks and system air
flow. Processor ‘power limit 2’ can be used as appropriate to limit the current drawn by
the processor to prevent any external power supply unit issues. The ‘Power Limit 2’
should always be programmed to a value (typically 20%) higher than ‘Power Limit 1’
and has no default value associated with it.
Though this feature is disabled by default and external programming is required to
enable, initialize and control package power limit values and time windows, the
processor package will still turbo to TDP if ‘Power Limit 1’ is not enabled or initialized.
‘Control Time Window#1’ (Power_Limit_1_Time also known as Tau) values may be
programmed to be within a range of 250 mS-40 seconds. ‘Control Time Window#2’
(Power_Limit_2_Time) values should be in the range 3 mS-10 mS.
The same conversion formula used for the DRAM Power Limiting feature (see
Section 2.5.2.6.9) should be applied when programming the ‘Control Time Window’ bits
[23:17] for ‘power limit 1’ in Figure 2-36. The ‘Control Time Window’ for ‘power limit 2’
can be directly programmed into bits [55:49] in units of mS without the aid of any
conversion formulas.
2.5.2.6.27 Package Power Limit Performance Status Read
This service allows the PECI host to assess the performance impact of the currently
active power limiting modes. The read return data contains the total amount of time for
which the entire processor package has been operating in a power state that is lower
than what the operating system originally requested. This information is tracked by a
32-bit counter that wraps around. The unit for time is determined as per the Package
Power SKU Unit settings described in Section 2.5.2.6.13.
Figure 2-36. Package Turbo Power Limit Data
Package Power Limit 1
Power Limit
Enable #1
1523
Power Limit # 1
14 0
Clamp
Mode #1
16
Control Time
Window #1
1731
RESERVED
24
Package Power Limit 2
Power Limit
Enable #2
4755
Power Limit # 2
46 32
Clamp
Mode #2
48
Control Time
Window #2
4963
RESERVED
56
Figure 2-37. Package Power Limit Performance Data
Accumulated CPU Throttle Time
Accumulated CPU Throttle Time
0
31