1.  Field of Invention
The present invention relates to a computer case, and more particularly to a dual-board case for a multi-mainboard system. 
2.  Description of the Related Art
With the highly modularized blade architecture, a blade server has the advantages of high density, convenient management, easy expansion, and suitable for special applications.  Generally speaking, the blade architecture is one of the best choices for high performance computing (HPC) systems.  However, a HPC system produces more heat than general systems while the high density blade architecture reduces the heat-dissipation efficiency.  Currently, some of the HPC systems adopt a liquid cooling system that provides high heat-dissipation efficiency.  However, when the liquid cooling system effectively enhances heat-dissipation efficiency, it also increases the complication and cost in manufacturing the HPC system. 
FIG.  1 shows a conventional personal supercomputer adopting the blade architecture.  The personal supercomputer with blade architecture is particularly designed for performing small-scaled but highly complicate computing.  As shown in FIG.  1, the personal supercomputer with blade architecture has several mainboards 110 parallelly arranged in a front inner space of a computer case 100.  The parallelly arranged mainboards 110 divide the front inner space of the computer case 100 into several sub-spaces to serve as airflow passages, just like a common blade architecture.  In a rear lower inner space of the computer case 100, a power supply with fan 120 is mounted.  And, in a rear upper inner space of the computer case 100, several main fans 130 are mounted to serve as a major cooling airflow source.  Airflow 140 sucked into the computer case 100 via a front end thereof passes through each of the sub-spaces and the main fans 130 to finally flow out of the computer case 100 via a rear end thereof. 
A big problem with the above-described arrangement is the narrow sub-spaces in the computer case 100 form a big hindrance to good heat dissipation.  Meanwhile, noise is produced due to collision of air molecules with different elements mounted in the computer case 100.  The spaced narrow airflow passages with uneven surfaces tend to cause more turbulences and louder whooshing sound.  For air to smoothly flow in the spaced narrow airflow passages with sufficient air pressure to pass through all small spaces between any two adjacent radiation fins 111 provided on the multiple mainboards 110, small-size fans with high rotary speed must be used.  These high-speed small fans also produce high decibel (dB) noise during operation thereof.  Moreover, since the multiple mainboards 110 are parallelly spaced in the front inner space of the computer case 100 to face toward the same direction, the radiation fins 111 on each of the mainboards 110 have a length being limited by a distance between two adjacent mainboards 110.  In other words, when it is desired to increase the size of fans 130 or the length of radiation fins 111, an overall width of the computer case 100 would inevitably be increased correspondingly.  Therefore, it is rather difficult to obtain enhanced heat-dissipation efficiency by increasing the size of the radiation fins 111 in the HPC systems adopting the blade architecture.