Intel 521 Data Sheet - Page 81

Datasheet

81

Thermal Specifications and Design Considerations

The PROCHOT# signal is asserted when a high temperature situation is detected, regardless of

whether or not Thermal Monitor or Thermal Monitor 2 is enabled.

It should be noted that the Thermal Monitor 2 TCC can not be activated via the on demand mode.

The Thermal Monitor TCC, however, can be activated through the use of the on demand mode.

5.2.3

On-Demand Mode

The Pentium 4 processor in the 775-land package 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 Thermal Monitor feature. On-Demand

mode is intended as a means to reduce system level power consumption. Systems using the

Pentium 4 processor in the 775-land package must not rely on software usage of this mechanism to

limit the processor temperature.

If bit 4 of the ACPI P_CNT Control Register (located in the processor IA32_THERM_CONTROL

MSR) is written 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 3:1 of the same ACPI P_CNT Control Register. In On-Demand mode, the

duty cycle can be programmed from 12.5% on/ 87.5% off, to 87.5% on/12.5% off in 12.5%

increments. On-Demand mode may be used in conjunction with the Thermal Monitor. 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.

Figure 5-4. Thermal Monitor 2 Frequency and Voltage Ordering

VID

Frequency

Temperature

T

TM2

f

MAX

f

TM2

VID

VID

TM2

PROCHOT#

Time

Section	Page
Contents	3
Revision History	7
Intel® Pentium® 4 Processors 570/571, 560/561, 550/551, 540/541, 530/531, and 520/521	9
1 Introduction	11
1.1 Terminology	12
1.1.1 Processor Packaging Terminology	12
1.2 References	13
2 Electrical Specifications	15
2.1 FSB and GTLREF	15
2.2 Power and Ground Lands	15
2.3 Decoupling Guidelines	15
2.3.1 VCC Decoupling	16
2.3.2 FSB GTL+ Decoupling	16
2.3.3 FSB Clock (BCLK[1:0]) and Processor Clocking	16
2.4 Voltage Identification	17
2.4.1 Phase Lock Loop (PLL) Power and Filter	19
2.5 Reserved, Unused, FC and TESTHI Signals	20
2.6 FSB Signal Groups	21
2.7 GTL+ Asynchronous Signals	22
2.8 Test Access Port (TAP) Connection	23
2.9 FSB Frequency Select Signals (BSEL[2:0])	23
2.10 Absolute Maximum and Minimum Ratings	24
2.11 Processor DC Specifications	24
2.12 VCC Overshoot Specification	33
2.12.1 Die Voltage Validation	33
2.13 GTL+ FSB Specifications	34
3 Package Mechanical Specifications	35
3.1 Package Mechanical Drawing	35
3.2 Processor Component Keep-Out Zones	39
3.3 Package Loading Specifications	39
3.4 Package Handling Guidelines	39
3.5 Package Insertion Specifications	40
3.6 Processor Mass Specification	40
3.7 Processor Materials	40
3.8 Processor Markings	40
3.9 Processor Land Coordinates	41
4 Land Listing and Signal Descriptions	43
4.1 Processor Land Assignments	43
4.2 Alphabetical Signals Reference	66
5 Thermal Specifications and Design Considerations	75
5.1 Processor Thermal Specifications	75
5.1.1 Thermal Specifications	75
5.1.2 Thermal Metrology	79
5.2 Processor Thermal Features	79
5.2.1 Thermal Monitor	79
5.2.2 Thermal Monitor 2	80
5.2.3 On-Demand Mode	81
5.2.4 PROCHOT# Signal	82
5.2.5 THERMTRIP# Signal	82
5.2.6 TCONTROL and Fan Speed Reduction	82
5.2.7 Thermal Diode	83
6 Features	85
6.1 Power-On Configuration Options	85
6.2 Clock Control and Low Power States	85
6.2.1 Normal State	86
6.2.2 HALT and Enhanced HALT Powerdown States	86
6.2.2.1 HALT Powerdown State	86
6.2.2.2 Enhanced HALT Powerdown State	86
6.2.3 Stop-Grant State	87
6.2.4 Enhanced HALT Snoop or HALT Snoop State, Grant Snoop State	88
6.2.4.1 HALT Snoop State, Grant Snoop State	88
6.2.4.2 Enhanced HALT Snoop State	88
7 Boxed Processor Specifications	89
7.1 Mechanical Specifications	90
7.1.1 Boxed Processor Cooling Solution Dimensions	90
7.1.2 Boxed Processor Fan Heatsink Weight	91
7.1.3 Boxed Processor Retention Mechanism and Heatsink Attach Clip Assembly	91
7.2 Electrical Requirements	91
7.2.1 Fan Heatsink Power Supply	91
7.3 Thermal Specifications	93
7.3.1 Boxed Processor Cooling Requirements	93

Intel 521 Data Sheet - Page 81

On-Demand Mode

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