Intel CM8062101038606, E5-4600, E5-2600, E5-1600 On-Demand Mode, Prochotn Signal, Clock Modulation

5.2.2.2Clock Modulation

Clock modulation is performed by alternately turning the clocks off and on at a duty cycle specific to the processor (factory configured to 37.5% on and 62.5% off for TM1). The period of the duty cycle is configured to 32 microseconds when the TCC is active. Cycle times are independent of processor frequency. A small amount of hysteresis has been included to prevent rapid active/inactive transitions of the TCC when the processor temperature is near its maximum operating temperature. Once the temperature has dropped below the maximum operating temperature, and the hysteresis timer has expired, the TCC goes inactive and clock modulation ceases. Clock modulation is automatically engaged as part of the TCC activation when the Frequency/ SVID targets are at their minimum settings. It may also be initiated by software at a configurable duty cycle.

5.2.3On-Demand Mode

The processor provides an auxiliary mechanism that allows system software to force the processor to reduce its power consumption. This mechanism is referred to as “On- Demand” mode and is distinct from the Adaptive Thermal Monitor feature. On-Demand mode is intended as a means to reduce system level power consumption. Systems must not rely on software usage of this mechanism to limit the processor temperature. If bit 4 of the IA32_CLOCK_MODULATION MSR is set to a ‘1’, the processor will immediately reduce its power consumption via modulation (starting and stopping) of the internal core clock, independent of the processor temperature. When using On- Demand mode, the duty cycle of the clock modulation is programmable via bits 3:0 of the same IA32_CLOCK_MODULATION MSR. In On-Demand mode, the duty cycle can be programmed from 6.25% on / 93.75% off to 93.75% on / 6.25% off in 6.25% increments. On-Demand mode may be used in conjunction with the Adaptive Thermal Monitor; however, if the system tries to enable On-Demand mode at the same time the TCC is engaged, the factory configured duty cycle of the TCC will override the duty cycle selected by the On-Demand mode.

5.2.4PROCHOT_N Signal

An external signal, PROCHOT_N (processor hot), is asserted when the processor core temperature has reached its maximum operating temperature. If Adaptive Thermal Monitor is enabled (note it must be enabled for the processor to be operating within specification), the TCC will be active when PROCHOT_N is asserted. The processor can be configured to generate an interrupt upon the assertion or de-assertion of PROCHOT_N.

The PROCHOT_N signal is bi-directional in that it can either signal when the processor (any core) has reached its maximum operating temperature or be driven from an external source to activate the TCC. The ability to activate the TCC via PROCHOT_N can provide a means for thermal protection of system components.

As an output, PROCHOT_N will go active when the processor temperature monitoring sensor detects that one or more cores has reached its maximum safe operating temperature. This indicates that the processor Thermal Control Circuit (TCC) has been activated, if enabled. As an input, assertion of PROCHOT_N by the system will activate the TCC, if enabled, for all cores. TCC activation due to PROCHOT_N assertion by the system will result in the processor immediately transitioning to the minimum frequency and corresponding voltage (using Freq/SVID control). Clock modulation is not activated in this case. The TCC will remain active until the system de-asserts PROCHOT_N.

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