Scalable disambiguating accesses in multi-level cache hierarchies provides
for improved system performance and reduced cost. Shared-storage provides portions
to hold data and portions to hold corresponding status encodings. Status encodings
provide information to disambiguate data requests to shared-storege without resorting
to prior methods of snooping or transmitting backward status-inquiries to private-storage.
Shared-storage transmits data in response to requests if its status encodings indicate
no private copies of the requested data have been modified. Shared storage transmits
data requests to private storage if corresponding status encodings indicate that
copies of requested data in private storage have been modified. Private-storage
provides coherent copies, and shared-storage proceeds to satisfy the requests.
If requests indicate a need to modify data, shared storage provides invalidation
transmissions to private storage holding copies of relevant data. Status encodings
are then set to a dirty status for coherently processing future requests.