![](http://datasheet.mmic.net.cn/160000/BX80532PC2500D_datasheet_8447585/BX80532PC2500D_75.png)
Intel Pentium 4 Processor on 0.13 Micron Process Datasheet
75
Features
cause a noticeable performance loss, and in some cases may result in a TC that exceeds the
specified maximum temperature and may affect the long-term reliability of the processor. In
addition, a thermal solution that is significantly under-designed may not be capable of cooling the
processor even when the TCC is active continuously. Refer to the Intel Pentium 4 Processor
with 512-KB L2 Cache on 0.13 Micron Process Thermal Design Guidelines for information on
designing a thermal solution.
The duty cycle for the TCC, when activated by the Thermal Monitor, is factory configured and
cannot be modified. The Thermal Monitor does not require any additional hardware, software
drivers, or interrupt handling routines.
The TCC may also be activated via On-Demand mode. If bit 4 of the ACPI Thermal Monitor
Control Register is written to a 1, the TCC will be activated immediately independent of the
processor temperature. When using On-Demand mode to activate the TCC, the duty cycle of the
clock modulation is programmable via bits 3:1 of the same ACPI Thermal Monitor Control
Register. In automatic mode, the duty cycle is fixed. However, 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 at the same time Automatic mode is enabled. However, if the
system tries to enable the TCC via On-Demand mode at the same time automatic mode is enabled
AND a high temperature condition exists, the duty cycle of the automatic mode will override the
duty cycle selected by the On-Demand mode.
An external signal, PROCHOT# (processor hot), is asserted when the processor detects that its
temperature is at the thermal trip point. Bus snooping and interrupt latching are also active while
the TCC is active. The temperature at which the thermal control circuit activates is not user
configurable and is not software visible.
Besides the thermal sensor and TCC, the Thermal Monitor feature also includes one ACPI register,
performance monitoring logic, bits in three model specific registers (MSR), and one I/O pin
(PROCHOT#). All are available to monitor and control the state of the Thermal Monitor feature.
Thermal Monitor can be configured to generate an interrupt upon the assertion or de-assertion of
PROCHOT#.
If automatic mode is disabled, the processor will be operating out of specification. Regardless of
enabling of the automatic or On-Demand modes, in the event of a catastrophic cooling failure the
processor automatically shuts down when the silicon has reached a temperature of approximately
135 °C. At this point the system bus signal THERMTRIP# goes active and stays active until
RESET# has been initiated. THERMTRIP# activation is independent of processor activity and
does not generate any bus cycles. If THERMTRIP# is asserted, processor core voltage (VCC) must
be removed within 0.5 seconds.