Thermally Advantaged Tested Chassis Guide

Introduction
E34579 / TAC 2.0 Design Guide 5
1 Introduction
1.1 Scope
This design guide explores the design and performance of a generic airflow
management scheme to adequately cool the internal components of a personal
computer. Design recommendations are presented for implementation within mid-
tower and mini-tower desktop style enclosures. The target audiences for this
document are: computer enclosure engineers, designers, and system integrators.
1.2 Overview
In order to facilitate next generation PC platform designs for 2009 and beyond, it has
become necessary to alter the physical location of the processor relative to previous
platform generations. Earlier versions of the Chassis Air Guide (CAG) Design Guide
presented a reference airflow management scheme that was dependant on a relatively
consistent location of the processor. The TAC 2.0 design guide accommodates this
change in processor location and provides backward compatibility to previous PC
platform generations.
Improvements in processor architecture design and reductions in transistor leakage
have resulted in more efficient processors that consume less power with better
performance than earlier generations. The goal of previous CAG Design Guide versions
was to define a means to limit the processor inlet temperature to a maximum of 38 °C
to allow for the use of cost effective processor cooling devices. With the improvements
in latest generation processor designs and performance it is possible to design cost
effective processor cooling solutions with a higher inlet temperature. Therefore, In
addition to eliminating processor location dependency, the TAC 2.0 Design Guide also
defines a new processor cooling solution inlet temperature target of 40 °C.
The scope of the previous CAG Design Guide was centered on an enclosure side duct
that delivered cooler external air directly to the processor fan heatsink. This revised
design guide eliminates the duct and relies solely on optimized chassis venting and
airflow management. This not only eliminates the above mentioned processor location
dependency but also allows for PC enclosure cost reduction when compared to
previous CAG Design Guide versions.
Proper thermal management of PC enclosure design is critical to the performance and
functionality of internal PC components as well as achieving desirable acoustic noise
levels. There are many different ways to provide proper chassis thermal management.
The design approach described in the document is one such method that if
implemented correctly will provide a single, cost effective solution for a wide range of
PC platform generations.