Appeal No. 2002-1498
Application No. 09/042,202
In a reactive flow control manner, the destination node tracks
its own queues and sends a queue full signal to a sending node
when the queue is full. In a proactive flow control manner, the
sending node keeps track of the amount of queue space available
at the destination queue in the form of “credits” stored in a
credit register. Each credit corresponds to a number of entries
available at the destination queue. The sending node will then
only send data to the destination node when the sending node has
sufficient credit. When the destination node clears space in the
queue, the destination queue releases credits to the sender,
allowing the sender to send more data, as needed. The
destination queue stores the number of credits to be released in
the debit register.
The problem lies in the initialization of credits in
respective registers. Since queue sizes may change over time,
with design revisions, the sender nodes cannot assume queue sizes
in a destination node. Therefore, upon start-up, the sender will
not know how many credits to allocate in the registers for each
queue in the destination node. While the prior art initially set
the debit and credit registers to zero and then software was used
to read the maximum number of credits for each destination node
and the number was written into the sender node, the problem
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