Intel® Pentium® 4 Processor in the 478-Pin Package Processor Power Distribution Guidelines
R
Intel
®
Pentium
®
4 Processor / Intel
®
850 Chipset Family Platform Design Guide 221
Table 52. Airflow Requirements
Design Example Minimum Airflow Notes
Three-Phase 110 LFM 1
Four-Phase 0 LFM 2
NOTES:
1. Assumes dedicated fan for Voltage Regulator (VR).
2. Assumes expanded layout area as compared to the three-phase VR design.
11.2.3 FMB2 - Voltage Regulator Thermal Protection Circuit
Intel recommends that the 845 and 850 chipset system boards be designed to support the full Intel
®
Pentium
®
4 Processor with 512-KB L2 Cache on 0.13 Micron Process FMB2 Guidelines. These
guidelines include an ICC_MAX of 70 A and a VR_TDC (VR thermal design Current) of 63 A.
The processor voltage regulator (VR) solution should be designed to support the ICC_MAX of
70 A electrically for brief time periods. The voltage regulator solution should also be designed to
support a minimum of 63 A VR_TDC indefinitely within the envelope of operating conditions of
the system. The VR_TDC limits of the system board are typically governed by the system board
thermal limits. Intel recommends that system boards designed to the above guidelines implement a
VR thermal monitor circuit.
Note: The specifications for the Pentium 4 processor with 512-KB L2 Cache on 0.13 micron process are
contained in the Intel
®
Pentium
®
4 Processor with 512-KB L2 Cache on 0.13 Micron Process
Processor Electrical, Mechanical, and Thermal Specifications (EMTS). In the event the above
numbers differ from the EMTS, the EMTS numbers should be considered correct.
The bi-directional PROCHOT# pin on the processor may be used to implement a thermal monitor
for the processor VR. When PROCHOT# is asserted by a VR thermal monitor the thermal control
circuit in the processor will activate and will reduce the current consumption of the processor. This
mechanism should only be used as a safety mechanism for the VR. The thermal monitor circuit
should not degrade the processor performance during normal operation. PROCHOT# should only
be asserted in the event of a failure that causes VR over temperature. In order for this type of
thermal monitor to act as a safety device for the system board, it is important that the thermal time
constant of the VR is longer than the thermal time constant of the processor combined with its
thermal solution.
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