The BusRDX operation is required even if the line is in the S state because even though you (as in the cache controller of the processor that wants to write) have an up-to-date version of the data and can immediately write, you have to let others know of your intentions so that they can invalidate their cache lines.
The
BusRDXoperation is required even if the line is in the S state because even though you (as in the cache controller of the processor that wants to write) have an up-to-date version of the data and can immediately write, you have to let others know of your intentions so that they can invalidate their cache lines.