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 23
Thermal/Mechanical Reference Design
Equation 2-7. Ψ
CA
= (T
CASE
– T
LA
) / TDP = (68 – 40) / 85 = 0.33 °C/W
It is evident from the above calculations that, a reduction in the local processor ambient
temperature has a significant positive effect on the case-to-ambient thermal resistance requirement.
2.3.3 Chassis Thermal Design Considerations
2.3.3.1 Chassis Thermal Design Capabilities and Improvements
One of the critical parameters in thermal design is the local ambient temperature assumption of the
processor. Keeping the external chassis temperature fixed, internal chassis temperature rise is the
only component that can affect the processor local ambient temperature. Every degree gained at the
local ambient temperature directly translates into a degree relief in the processor case temperature.
Given the thermal targets for the processor, it is extremely important to optimize the chassis design
to minimize the air temperature rise upstream to the processor (T
rise
), hence minimizing the
processor local ambient temperature.
The heat generated by components within the chassis must be removed to provide an adequate
operating environment for both the processor and other system components. Moving air through
the chassis brings in air from the external ambient environment and transports the heat generated
by the processor and other system components out of the system. The number, size and relative
position of fans, vents and other heat generating components determine the chassis thermal
performance, and the resulting ambient temperature around the processor. The size and type
(passive or active) of the thermal solution and the amount of system airflow can be traded off
against each other to meet specific system design constraints. Additional constraints are board
layout, spacing, component placement, and structural considerations that limit the thermal solution
size.
In addition to passive heatsinks, fan heatsinks and system fans, other solutions exist for cooling
integrated circuit devices. For example, ducted blowers, heat pipes and liquid cooling are all
capable of dissipating additional heat. Due to their varying attributes, each of these solutions may
be appropriate for a particular system implementation.
To develop a reliable, cost-effective thermal solution, thermal characterization and simulation
should be carried out at the entire system level, accounting for the thermal requirements of each
component. In addition, acoustic noise constraints may limit the size, number, placement, and types
of fans that can be used in a particular design.
2.4 Thermal/Mechanical Reference Design
Considerations
2.4.1 Heatsink Solutions
2.4.1.1 Heatsink Design Considerations
To remove the heat from the processor, three basic parameters should be considered:
• The area of the surface on which the heat transfer takes place - Without any
enhancements, this is the surface of the processor package IHS. One method used to improve
thermal performance is by attaching a heatsink to the IHS. A heatsink can increase the