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6.2.5
THERMTRIP# Signal
Regardless of whether or not Thermal Monitor or Thermal Monitor 2 is enabled, in the
event of a catastrophic cooling failure, the processor will automatically shut down when
the silicon has reached an elevated temperature (refer to the THERMTRIP# definition in
Table
5-1). At this point, the FSB signal THERMTRIP# will go active and stay active as
described in
does not generate any bus cycles. Intel also recommends the removal of V
6.3
Platform Environment Control Interface (PECI)
6.3.1
Introduction
The introduction of the Dual-Core Intel
transition from thermal diodes to digital thermal sensors for fan speed control. Digital
Thermal Sensors (DTS) are on-die, analog-to-digital temperature converters calibrated
at the factory for reasonable accuracy to provide a digital representation of relative
processor temperature. Data from the DTS are processed and stored in a processor
register which is queried through the Platform Environment Control Interface (PECI).
PECI is a proprietary one-wire bus interface that provides a communication channel
between Intel processor and chipset components to external thermal monitoring
devices. A topology diagram is given in
• A wide speed range from 2 Kbps to 2 Mbps.
• CRC check byte used to efficiently and automatically confirm accurate data delivery
• Synchronization at the beginning of every message minimizes device timing
accuracy requirements
The Platform Environment Control Interface (PECI) bus uses a single wire for self-
clocking and data transfer, and requires no additional control lines. The physical layer
is a self-clocked one-wire bus that begins each bit with a driven, rising edge from an
idle level near zero volts. The duration of the signal driven high depends on whether
the bit value is a logic '0' or logic '1'. PECI also includes variable data transfer rate
established with every message. The single wire interface provides low board routing
overhead for the multiple load connections in the congested routing area near the
processor and chipset components.
overhead provides adequate link bandwidth and reliability to transfer critical device
operating conditions and configuration information.
Note:
The PECI interface is disabled by default, and must be enabled through BIOS by setting
PECI_EN (bit 0 of Model Specific Register PECI_CTL at address 05A0h) to 1.
86
Table
5-1. THERMTRIP# activation is independent of processor activity and
®
®
Xeon
Processor 5100 Series marks the
Figure
6-7. The PECI bus offers:
Bus speed, error checking, and low protocol
®
®
Dual-Core Intel
Xeon
Thermal Specifications
.
TT
Processor 5100 Series Datasheet
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