Intel Pentium 4 Processor with 512-KB L2 Cache on 0.13 Micron Process Thermal Design Guidelines

Thermal Specifications

Intel

Pentium

4 Processor Thermal Design Guide 37

A system designed to meet the TDP and T

targets published in the Intel

Pentium

4 Processor

with 512-KB L2 Cache on 0.13 Micron Process Datasheet greatly reduces the probability of real

applications causing the thermal control circuit to activate under normal operating conditions.

Systems that do not meet these specifications could be subject to frequent activation of the thermal

control circuit depending upon ambient air temperature and application power profile. Moreover,

if a system is significantly under designed, there is a risk that the Thermal Monitor feature will not

be capable of maintaining a safe operating temperature and the processor could shutdown and

signal THERMTRIP#.

For information regarding THERMTRIP#, refer to Section 3.4.7.2 and to the processor datasheet.

3.4.6 Operating System and Application Software

Considerations

The Thermal Monitor feature and its thermal control circuit work seamlessly with ACPI compliant

operating systems. The Thermal Monitor feature is transparent to application software since the

processor bus snooping, ACPI timer, and interrupts are active at all times.

Activation of the thermal control circuit during a non-ACPI aware operating system power-on

process may result in incorrect calibration of operating system software timing loops. The BIOS

must disable the thermal control circuit prior to power-on and then the operating system or BIOS

must enable the thermal control circuit after the operating system power-on process completes.

Intel is working with the major operating system (OS) suppliers to ensure support for non-

execution based operating system calibration loops and ACPI support for the Thermal Monitor

feature. Per Microsoft, Microsoft Windows* 98SE, and Windows* 2000 operating systems use

non-execution based calibration loops and therefore should have no issues with the Thermal

Monitor feature. When installing Microsoft Windows NT* 4.0 operating system, the user must

ensure the APIC-based HAL is used. It is expected that other operating system solutions (Linux*,

Unix*, etc.) will provide updates to ensure compatibility.

3.4.7 Legacy Thermal Management Capabilities

In addition to Thermal Monitor, the Pentium 4 processor with 512-KB L2 cache on 0.13 micron

process supports the same thermal management features as available on the Intel

Pentium

III

processor. These features are the on-die thermal diode and THERMTRIP# signal for indicating

catastrophic thermal failure.