A packet classification system, methods, and corresponding apparatus are provided for enabling packet classification. A key is input, a hash function is performed on the key, a direct table is accessed, and a tree is walked through pattern search control blocks until reaching a leaf. The first area is provided with a first heat exchanger and a ventilating blower. To retract the needle from the opening, the horizontal portion of the needle, which may be encased in an arm, is rotated about the upright to which it is hingedly connected so that the needle is pivoted upwards and withdrawn from the opening. Setting the lower limit to be equal to the upper limit forces overclocking to occur at only the specified value.