Intel® Xeon® Processor E5-1600/E5-2600/E5-4600 Product Families 141
Datasheet Volume One
PROCHOT_N can allow voltage regulator (VR) thermal designs to target maximum
sustained current instead of maximum current. Systems should still provide proper
cooling for the VR, and rely on PROCHOT_N as a backup in case of system cooling
failure. The system thermal design should allow the power delivery circuitry to operate
within its temperature specification even while the processor is operating at its Thermal
Design Power.
With a properly designed and characterized thermal solution, it is anticipated that
PROCHOT_N will be asserted for very short periods of time when running the most
power intensive applications. An under-designed thermal solution that is not able to
prevent excessive assertion of PROCHOT_N in the anticipated ambient environment
may cause a noticeable performance loss. Refer to the appropriate platform design
guide and for details on implementing the bi-directional PROCHOT_N feature.
5.2.5 THERMTRIP_N Signal
Regardless of whether Adaptive Thermal Monitor 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_N definition in
Section 6, “Signal Descriptions”). At this point, the THERMTRIP_N signal will go active
and stay active. THERMTRIP_N activation is independent of processor activity and does
not generate any Intel QuickPath Interconnect transactions. If THERMTRIP_N is
asserted, all processor supplies (VCC, VTTA, VTTD, VSA, VCCPLL, VCCD) must be
removed within the timeframe provided. The temperature at which THERMTRIP_N
asserts is not user configurable and is not software visible.
5.2.6 Integrated Memory Controller (IMC) Thermal Features

5.2.6.1 DRAM Throttling Options

The Integrated Memory Controller (IMC) has two, independent mechanisms that cause
system memory throttling:
• Open Loop Thermal Throttling (OLTT) and Hybrid OLTT (OLTT_Hybrid)
• Closed Loop Thermal Throttling (CLTT) and Hybrid CLTT (CLTT_Hybrid)
5.2.6.1.1 Open Loop Thermal Throttling (OLTT)
Pure energy based estimation for systems with no BMC or Intel ME. No memory
temperature information is provided by the platform or DIMMs. The CPU is informed of
the ambient temperature estimate by the BIOS or by a device via the PECI interface.
DIMM temperature estimates and bandwidth control are monitored and managed by
the PCU on a per rank basis.
5.2.6.1.2 Hybrid Open Loop Thermal Throttling (OLTT_Hybrid)
Temperature information is provided by the platform (for example, BMC or Intel®
Management Engine (Intel® ME)) through PECI and the PCU interpolates gaps with
energy based estimations.
5.2.6.1.3 Closed Loop Thermal Throttling (CLTT)
The processor periodically samples temperatures from the DIMM TSoD devices over a
programmable interval. The PCU determines the hottest DIMM rank from TSoD data
and informs the integrated memory controller for use in bandwidth throttling decisions.