Managing the resources processing data transfers in input/output chips using a FIFO memory to hold the details of resources that have been timed out

Disclosed is a system for managing the resources processing data transfers in a transaction based input/output chip of a computer system. A transaction is associated with a resource, 18 the transaction being a request packet and a corresponding response packet. The system has a transaction table 10 for holding one resource for each request until the resource has been processed and a resource management 12 for storing information about the availability of these resources, which has become available before a predetermined timeout period T has been exceeded. The system has a FIFO (first-in first-out) memory 14 for buffering those resources, which have been made available after the first timeout period and a second timeout period Q have been exceeded. An arbiter circuit 16 for chooses the resources from the resource management, if any are available, if not the timed-out resources from the FIFO memory are used.