Cpu Thermal Trip Points; Table 22: Cpu Thermal Trip Points - VersaLogic Blackbird VL-EPU4562 Hardware Reference Manual

The decision which thermal solution to use relies on several factors including:
Number of CPU cores in the SoC (single, dual, or quad)

CPU and video processing utilization by the user application

Temperature range within which the EPU-4562/4462 will be operated

Air movement (or lack of air movement)

Most of these factors involve the demands of the user application on the EPU-4562/4462 and
cannot be isolated from the overall thermal performance. Due to the interaction of the user
application, the Blackbird thermal solution, and the overall environment of the end system,
thermal performance cannot be rigidly defined.
The ambient air surrounding the EPU-4562/4462 needs to be maintained at 85 ºC or below. This
would include the space between the two main boards as well as the space beneath an installed
Mini PCIe expansion board. Standard methods for addressing this requirement include the
following:
Provide a typical airflow of 100 linear feet per minute (LFM) / 0.5 linear meters per second

(as described in the section titled EPU-4562/4462 Thermal Characterization, beginning on
page 68) within the enclosure
Position the EPU-4562/4462 board to allow for convective airflow

Lower the system level temperature requirement as needed


CPU Thermal Trip Points

The CPU cores in the Blackbird have their own thermal sensors. Coupled with these sensors are
specific reactions to three thermal trip points. The table below describes the three thermal trip
points. Note that these are internal temperatures that are about 10 ºC above the heat plate
temperature.

Table 22: CPU Thermal Trip Points

Trip Point
Passive (Note 1)
Critical (Note 2)
Maximum core temperature
Notes:
1. The default value in the BIOS Setup utility for this trip point is 90 ºC.
2. The default value in the BIOS Setup utility for this trip point is 100 ºC.
These trip points allow maximum CPU operational performance while maintaining the lowest
CPU temperature possible. The long-term reliability of any electronic component degrades when
it is continually run near its maximum thermal limit. Ideally, the CPU core temperatures will be
kept well below 100 ºC with only brief excursions above.
VL-EPU-4562/4462 Reference Manual
At this temperature, the CPU cores throttle back to a lower speed. This
reduces the power draw and heat dissipation, but lowers the processing
speed.
At this temperature, the operating system typically puts the board into a
sleep or other low-power state.
The CPU turns itself off when this temperature is reached. This is a fixed
trip point and cannot be adjusted.
Thermal Considerations
Description
65