A system control apparatus and method capable of increasing the
possibility of recovery from a synchronization error in snooping between
system controllers are provided. The system control apparatus has a local
port that holds a memory access request received externally and reoutputs
it in response to an error retry instruction. A broadcast output section
broadcasts the memory access request. A broadcast input section receives
the broadcast memory access request. A global port holds the received
memory access request. A snoop control section transmits and receives
cache status information containing a result of snooping, and detects a
synchronization error on the basis of the cache status information. If a
synchronization error occurs, the snoop control section outputs the error
retry instruction to the local port holding the memory access request
that resulted in the synchronization error.