Optimizing the performance of asynchronous bus bridges with dynamic transactions

A system for completing a present read transaction between an initiator device and a host memory device in a computer system, said system comprising:

• a bus;
• a bus bridge device, said bus bridge device comprising:
• a target device, said target device coupled to said initiator device via said bus;
• and
• a timer mechanism coupled to said target device, wherein said timer mechanism is also coupled to said initiator device;
• and
• said host memory device coupled to said bus bridge device;
• said timer mechanism adapted to measure target latency for one or more read transactions contiguously preceding said present read transaction, said timer mechanism further adapted to use said target latency to determine a dynamic target latency period and to update said dynamic target latency period after each read transaction;
• and
• said initiator device adapted to delay a retry of said access until said dynamic target latency period is exceeded.

In a peripheral component interconnect (PCI) bus system comprising a PCI initiator device coupled to a host memory device via a bus bridge device, said bus bridge device comprising a timer mechanism coupled to a PCI target device, a method for completing a present read transaction between said PCI initiator device and said host memory device, said method comprising the steps of:

• a) said timer mechanism measuring target latencies for one or more read transactions contiguously preceding said present read transaction, said timer mechanism coupled to said PCI target device;
• b) said timer mechanism determining a dynamic target latency period using said target latencies;
• wherein said dynamic target latency period is updated after each read transaction;
• and
• c) said PCI initiator device asserting an access, such that said present read transaction is initiated;
• d) said PCI target device claiming said access;
• e) using said dynamic target latency period to specify when said access is to be retried.