METHOD FOR REDUCING CROSS-INTERROGATE DELAYS IN A MULTIPROCESSOR SYSTEM

A Fetch-Then-Confirm (FTC) policy is used for the handling of data fetch upon XIEX's in a tightly coupled multiprocessor environment. The fetch and/or use of a requested data line upon XIEX is allowed before the SCE receives the confirmation of validity (or invalidity) of the requested line through the clearing procedure. Whenever a line having uncertain validity is used by a CP the results of execution of instructions depending on the validity of the line should not be committed to the cache until a confirmation is received from the SCE. When the confirmation from the SCE indicates that a line L is known to be valid, all results depending on the validity of L can be processed as usual. If, however, the SCE indicates that a previously fetched line L having uncertain validity is in fact invalid, all operations performed based on L's contents should be aborted and restarted properly when a valid copy of L is received.