Distributed fairness protocol for interconnect networks

A method, comprising:

• generating, by a data processing node, a plurality of data transactions, wherein a destination of a first data transaction of the plurality of data transactions is a particular circuit node of a plurality of circuit nodes;
• determining, by the data processing node, an availability of an access unit coupled to the data processing node;
• in response to determining that the access unit is available, transferring the first data transaction to the access unit;
• and
• in response to determining that the access unit is unavailable:
• halting a transfer of remaining data transactions of the plurality of data transactions to the access unit;
• and
• transmitting a halt indicator signal via a physical connection between the data processing node and a different data processing node that is coupled to a different access unit.

An apparatus, comprising:

• a logic node configured to generate a plurality of data transactions, wherein a destination of a particular data transaction of the plurality of data transactions is a particular circuit node;
• a queue coupled to an access unit;
• and
• an access interface configured to:
• store a next data transaction of the plurality of data transactions in the queue in response to a determination that the queue has available storage space;
• and
• in response to a determination that the queue is full:
• halt storage of the plurality of data transactions;
• and
• assert at least one halt indicator signal on a physical connection between the access interface and a different access interface.

A system, comprising:

• a plurality of access units, each access unit of the plurality of access units coupled to at least one other access unit of the plurality of access units, wherein a particular access unit of the plurality of access units is configured to transfer a data transaction to a coupled access unit in response to a transfer signal;
• a plurality of circuit nodes each coupled to a respective one of the plurality of access units;
• and
• a plurality of data processing nodes each coupled to a respective access unit of the plurality of access units, wherein a particular data processing node is configured to transfer a data transaction to the particular access unit, wherein a destination of the data transaction is a particular circuit node of a plurality of circuit nodes;
• wherein the particular access unit is further configured to:
• reject the transfer of the data transaction from the particular data processing node in response to a determination that the particular access unit is unavailable;
• increment a count value in response to the rejection of the transfer of the data transaction;
• and
• assert a stall request signal to a different access unit of the plurality of access units in response to a determination that the count value has satisfied a threshold;
• and
• wherein the different access unit is configured to halt transfer of data transactions from another data processing node of the plurality of data processing nodes in response to detecting the asserted stall request signal.