CCSI's Cooling Technology
'The Challenge'

The introduction in June of 2001 of dual Athlon system boards by Tyan not only "raised the bar" of computing performance but also of thermal management. Conventional chassis and cooling solutions can simply no longer handle the thermal requirements. The magnitude of the problem becomes even greater when designing low profile, high-density, servers such as the 1U and 2U rackmount solutions

In conventional tower server chassis and in low-density rack chassis installations, there is ample real estate in the front and rear and on the sides of the chassis for mounting intake and exhaust fans. In contrast, the low-profile 1U and 2U rack space does not provide adequate room for exhaust fans. Furthermore, there is precious little room for intake and exhaust vents, which compromises fan performance, lowering their actual performance to significantly below their "rated" airflow capacity, which is designed for a minimal resistance (to airflow) environment. In fact the only exhaust system available on a conventional 1U or 2U chassis is the power supply exhaust fan which is totally inadequate to provide sufficient exhaust of hot air to allow the system to cool reliably. The result, of course, is an unstable and virtually useless system.

The thermal dilemma becomes even more critical when conventional fan top or blow through CPU coolers are used. The efficiency of all CPU coolers is linked directly to the temperature of the intake air. Every degree rise in intake air temperature to the CPU cooler directly translates into a corresponding rise in the CPU junction temperature.

In the conventional server chassis the warm exhaust air from the CPU cooler is re-circulated inside the chassis causing the CPU temperature to rise until it reaches a thermal equilibrium which is determined by the chassis's exhaust system capacity. In our tests at CCSI, we have seen CPU temperature rises of between 25 and 48 degrees centigrade in several conventional 1U and 2U chassis specimens that we have tested. This is easily observed with a simple cover on and then cover off test while running a CPU loading utility. Another major shortcoming of the conventional fan top CPU coolers is the reduction of airflow due to pressure drop resulting from the airflow obstruction of the chassis cover and the fins of the heat sink itself. Fans performance is rated in cubic feet per minute (CFM) with 0 pressure drop and performance is severely compromised with only minimal air flow obstructions from either the intake or exhaust side of the fan. The CCSI Wind Tunnel™ eliminates these problems.

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