3com Corporation

David James Mannion

James Scott Hiscock

Carl John Lindeborg

A computer network switch includes a receiving module for receiving packets, a packet memory with a plurality of buffer cells with each of the buffer cells having a buffer descriptor. A descriptor free pool lists available buffer descriptors that can be used for new incoming packets. A plurality of transmit queues hold the buffer descriptors. Each of the transmit queues include an input queue, an expansion queue and an output queue. The switch also includes control logic for directing the removing of one of the available buffer descriptors from the free pool and directing one of the packets from the receiving module into one of the buff cells corresponding to the one available buffer descriptor. The control logic places the one buffer descriptor in the input queue of one of the transmit queues. The control logic also monitors a load status of the input and output queues.

Transmit queue caching

A technique for encoding index values of asynchronous pointers for a non-power-of-two sized buffer that supports the unit distance property. The technique includes converting N&plus;1 pointer index values corresponding to index locations 0 through N of the buffer from the natural binary-coded decimal format to a unit distance code format such as the gray code, adding a 0 bit in the MSB position of each of the N&plus;1 converted pointer index values, adding a first pointer index value at index location N&plus;1 equal to the pointer index value at index location N except that a 1 bit replaces the 0 bit in the MSB position, and adding a plurality of pointer index values at index locations greater than N&plus;1 but less than or equal to N&plus;n&plus;1 that are equal to the first added pointer index value, where &ldquo;n&rdquo; equals the number of bits in each pointer index value prior to conversion. The 1 bits of the plurality of added pointer index values, starting with the LSB position and continuing with bit positions nearest the LSB, are then successively cleared until the pointer index value corresponding to the highest index location has a 1 bit in the MSB position and 0 bits in the remaining bit positions.

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Northboro, MA, United States of America

David James Mannion