Method and apparatus to provide pended transaction on a non-pended system bus

DETAILED DESCRIPTION In accordance with the present invention a data processing system includes a plurality of nodes connected to a shared data path, one of the plurality of nodes being a commander node to initiate a transaction on the shared data path, and one of the plurality of nodes being a responder node.
The present invention further includes means for providing, by the responder node, a response to the commander node indicating unavailability of the responder node and for providing an acknowledgement of the transaction over the shared data path and means, directly responsive to the response indicating that the responder node is unavailable to respond to the transaction, for retrying the transaction.
With such an arrangement, layering a hardware retry mechanism within the constructs of a non-pended bus, the problems of stalling and deadlock are avoided in a non-pended bus which does not support a retry mechanism.
This arrangement thus permits pended transactions (i.
e.
multiple transactions in progress at the same time) on a non-pended bus.
This is accomplished by permitting the I/O responding device to defer an access request (i.
e.
a read or write) until resources are cleared up and the transaction can complete.