The latest technology of personal computer, including processor, chipset, memory and graphics technology, poses a huge challenge to system designers in terms of heat dissipation. As the market moves towards higher computing speed, more powerful functions and smaller models, the heat and heat density generated by these devices will continue to increase. This increase in thermal energy at the component level forces designers to reconsider cooling solutions at the chip, packaging, motherboard and system levels. Passive and active radiators have proven to be a reliable and relatively economical solution, sufficient to keep up with the challenges of the growing thermal environment. In order to continue to use these heat sink technologies, it is necessary to consider the cooling scheme at the system level.
In the past, system designers focused on improving the thermal environment of the system by increasing the number of fans and optimizing the position of vents. This approach is still an important aspect of system cooling design. However, the cost and complexity of packaging level heat dissipation schemes are getting higher and higher, which requires more advanced system level technologies to find more balanced and cost-effective system countermeasures. If the shell of the computer can provide a lower internal temperature, this cost can be greatly saved. By properly balancing system level solutions with packaging level solutions, integrators can significantly reduce the total cost of the system. In an environment with increasing heat load, processors are usually the most demanding components for system cooling design. Processor cooling solutions typically use copper or aluminum heat sinks with active fans to promote air flow. The processor failure temperature can be directly related to the temperature of the air entering the active fans and radiators. The lower the air temperature, the lower the processor failure temperature. With the introduction of INTEL Prescott Pentium4 4 CPU above 3G, the high power consumption of high frequency processor has brought more heat, and the old chassis cooling scheme can no longer meet its needs. So INTEL has put forward a whole set of solutions to solve the heat dissipation and EMI prevention problems caused by CPU above 3G. The "Air Guide Design" is one of them, and the more significant one is the BTX specification. It also derived EMI proof Wave Guide Design and U-seam Design
Air Guide Design generated by 38 ℃
We all know that the temperature generated by the CPU surface is basically 72 ℃ (INTEL calls it T-case temperature), while at the ambient temperature of 35 ℃, the internal temperature environment provided by most computer cases is generally about 40-45 ℃. However, INTEL must ensure that the T-case temperature is controlled within 72 ℃. According to the heat dissipation capacity brought by the CPU fan, if the temperature rise in the chassis (called T-rise by INTEL) is lower than the target of 3 ℃, the temperature in the chassis must be controlled below the ambient temperature of 35 ℃ plus T-rise 3 ℃ equal to 38 ℃ (called T-ambient temperature by INTEL). The measurement method of this 38 ℃ is: the average temperature of 4 points 2 cm above the heat sink of the CPU fan. The forward and backward air flow direction of the chassis increases the temperature of the air flowing to the CPU fan a lot, so it is necessary to open a separate air duct for the CPU fan, so that the air temperature obtained by the CPU fan is exactly below 35 ℃, so the "chassis air duct" is generated.

    以往，系统设计师专注于通过增加风扇的数量和优化通风口的位置来改进系统的热环境。这一途径仍然是系统散热设计的一个重要方面。然而，包装层次散热方案的成本和复杂程度越来越高，要求有更先进的系统层次的技术，以发现更平衡、成本效益更佳的系统对策。如果计算机的外壳能提供较低的内部温度，就能大大节省这一开支。通过在系统层次解决方案和包装层次解决方案之间的恰当平衡，集成商可极大地降低系统的总成本。在热负荷越来越大的环境中，处理器通常是对系统散热设计要求最高的部件。处理器散热方案通常使用铜质或铝质的散热器，并以活跃的风扇促使空气流动。处理器失效温度可以与进入活跃的风扇和散热器的空气的温度有直接关系。空气温度越低，处理器失效温度也越低。随着INTEL Prescott Pentium4 3G以上CPU的推出后，因为高频处理器的高功耗带来了更大的发热量，而旧有的机箱散热方案已经无法满足其需求。于是INTEL为解决3G以上CPU所带来的散热及防EMI问题而提出了一整套的方案，“机箱导风管”的设计(Air Guide Design)就是其中一种，而更为显著的另外一套方案就是BTX的规范。并且也衍生出防EMI的Wave Guide Designe和U-seam Design

    由38℃而产生的Air Guide Design(机箱导风管设计)

    我们都知道CPU表面所产生的温度基本上是在72℃（INTEL称之为T-case温度），而在 35℃的环境温度下，大多数计算机机箱提供的机内温度环境一般约为 40-45℃。而INTEL必须保证T-case温度控制在72℃之内，根据CPU风扇所带来的散热能力，必须要让机箱内的升温(INTEL称之为T-rise)低于3℃的目标，就必须要求机箱内的温度控制在环境温度35℃加T-rise3℃等于38℃（此38℃ INTEL称之为T-ambient温度）之下。此38℃的测量方式是：CPU风扇散热片(heatsink)上方2cm高取4点的平均温度。而机箱的前进后出的空气流向，使得流向CPU风扇的空气温度已经有上升很多，所以就需要为CPU风扇单独开出一条风道，使得CPU风扇得到的空气温度正好是在35℃以下，所以就产生了“机箱导风管”。