Intel E5-4600, E5-2600 Package Power Limit Performance Status Read, Window #2 Mode #2 Enable #2

‘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.

Figure 2-36. Package Turbo Power Limit Data

63	56	55	49	48	47	46	32
	RESERVED	Control Time		Clamp	Power Limit		Power Limit # 2
		Window #2		Mode #2	Enable #2
				Package Power Limit 2
31	24	23	17	16	15	14	0
	RESERVED	Control Time		Clamp	Power Limit		Power Limit # 1
		Window #1		Mode #1	Enable #1

Package Power Limit 1

2.5.2.6.27Package 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 2-37. Package Power Limit Performance Data

31 0

Accumulated CPU Throttle Time

Accumulated CPU Throttle Time

Intel® Xeon® Processor E5-1600/E5-2600/E5-4600 Product Families	57
Datasheet Volume One