64-bit Intel Xeon Processor with 2MB L2 Cache Thermal/Mechanical Design Guidelines

64-bit Intel® Xeon™ Processor with 2MB L2 Cache Thermal/Mechanical Design Guidelines 71
Processor Thermal Management Logic and Thermal Monitor Features
E.1.3 Operation and Configuration
To maintain compatibility with previous generations of processors, which have no integrated
thermal logic, the TCC portion of Thermal Monitor is disabled by default. During the boot process,
the BIOS must enable the TCC; or a software driver may do this after the operating system has
booted. Thermal Monitor or Thermal Monitor 2 feature must be enabled for the processor to
remain within specification.
The TCC feature can be configured and monitored in a number of ways. OEMs are expected to
enable the TCC while using various registers and outputs to monitor the processor thermal status.
The TCC is enabled by the BIOS setting a bit in an MSR (model specific register). Enabling the
TCC allows the processor to maintain a safe operating temperature without the need for special
software drivers or interrupt handling routines. When the TCC has been enabled, processor power
consumption will be reduced within a few hundred clock cycles after the thermal sensor detects a
high temperature, i.e. PROCHOT# assertion. The TCC and PROCHOT# transition to inactive once
the temperature has been reduced below the thermal trip point, although a small time-based
hysteresis has been included to prevent multiple PROCHOT# transitions around the trip point.
External hardware can monitor PROCHOT# and generate an interrupt whenever there is a
transition from active-to-inactive or inactive-to-active. PROCHOT# can also be configured to
generate an internal interrupt which would initiate an OEM supplied interrupt service routine.
Regardless of the configuration selected, PROCHOT# will consistently indicate the thermal status
of the processor.
The TCC can also be activated manually using an “on-demand” mode.
E.1.4 Thermal Monitor 2
The 64-bit Intel Xeon Processor with 2MB L2 Cache also supports an enhanced TCC that works in
conjunction with the existing Thermal Monitor logic. This capability is known as Thermal Monitor
2. This improved TCC provides a more efficient means for limiting the processor temperature by
reducing the power consumption within the processor.
Note: Not all 64-bit Intel Xeon Processor with 2MB L2 Cache are capable of supporting Thermal
Monitor 2. Details on which processor frequencies support Thermal Monitor 2 are provided in the
NDA Preliminary 64-bit Intel
®
Xeon™ Processor with 800 MHz System Bus (1MB and 2MB L2
Figure E-2. Concept for Clocks under Thermal Monitor Control