Intel CM8062101038606, E5-4600, E5-2600 Package Power Limits For Multiple Turbo Modes, Mode Enable

compared to the input PROCHOT_N signal assertion method. Both power limit enabling and initialization of power limit values can be done in the same command cycle. Setting a power limit for the VCC plane enables turbo modes for associated logic. External VR protection is guaranteed during boot through operation at safe voltage and frequency. All RAPL parameter values including the power limit value, control time window, clamp mode and enable bit will have to be specified correctly even if the intent is to change just one parameter value when programming over PECI.

The usefulness of the VCC power plane RAPL may be somewhat limited if the platform has a fully compliant external voltage regulator. However, platforms using lower cost voltage regulators may find this feature useful. The VCC RAPL value is generally expected to be a static value after initialization and there may not be any use cases for dynamic control of VCC plane power limit values during run time. BIOS may be ideally used to read the VR (and associated heat sink) capabilities and program the PCU with the power limit information during boot. No matter what the method is, Intel recommends exclusive use of just one entity or interface, PECI for instance, to manage VCC plane power limiting needs. If PECI is being used to manage VCC plane power limiting activities, BIOS should lock out all subsequent inband VCC plane power limiting accesses by setting bit 31 of the PP0_POWER_LIMIT MSR and CSR to ‘1’.

The same conversion formula used for DRAM Power Limiting (see Section 2.5.2.6.9) should be applied for encoding or programming the ‘Control Time Window’ in bits [23:17].

Figure 2-35. Power Limit Data for VCC Power Plane

31	24	23	17	16	15	14	0
	RESERVED	Control Time		Clamp	Power Limit		VCC Plane Power Limit
		Window		Mode	Enable

VCC Power Plane Power Limit Data

2.5.2.6.26Package Power Limits For Multiple Turbo Modes

This feature allows the PECI host to program two power limit values to support multiple turbo modes. The operating systems and drivers can balance the power budget using these two limits. Two separate PECI requests are available to program the lower and upper 32 bits of the power limit data shown in Figure 2-36. The units for the Power Limit and Control Time Window are determined as per the Package Power SKU Unit settings described in Section 2.5.2.6.13 while the valid range for power limit values are determined by the Package Power SKU settings described in Section 2.5.2.6.14. Setting the Clamp Mode bits is required to allow the cores to go into power states below what the operating system originally requested. The Power Limit Enable bits should be set to enable the power limiting function. Power limit values, enable and clamp mode bits can all be set in the same command cycle. All RAPL parameter values including the power limit value, control time window, clamp mode and enable bit will have to be specified correctly even if the intent is to change just one parameter value when programming over PECI.

Intel recommends exclusive use of just one entity or interface, PECI for instance, to manage all processor package power limiting and budgeting needs. If PECI is being used to manage package power limiting activities, BIOS should lock out all subsequent inband package power limiting accesses by setting bit 31 of the PACKAGE_POWER_LIMIT MSR and CSR to ‘1’. The ‘power limit 1’ is intended to limit processor power consumption to any reasonable value below TDP and defaults to TDP.

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