Pseudo least-recently-used (PLRU) replacement method for a multi-node snoop filter

A Pseudo Least-Recently-Used (PLRU) replacement method for a multi-node Snoop Filter including a plurality of lines storing data information, comprising:

• determining if a processor transaction is one of a processor memory read (RM), a processor read for ownership (RO), a clean line replacement (CLR), and a processor write (W);
• determining if a Snoop Filter cache array has a line associated with the processor transaction, if the processor transaction is one of the processor memory read (RM) and the processor read for ownership (RO);
• if the cache array has a line associated with the processor transaction indicating a HIT condition, selecting a corresponding entry (way) as a most-recently used (MRU);
• if the cache array does not have a line associated with the processor transaction indicating a MISS condition, selecting a victim entry (way) using a LRU vector and making the victim entry (way) as MRU;
• and
• selecting a corresponding way as LRU, if the processor transaction is one of the clean line replacement (CLR) and the processor write (W).

A multi-node processor system, comprising:

• one or more processor nodes each including a plurality of processors with processor caches;
• one or more I/O nodes each including an I/O bridge with a private I/O cache;
• and
• a Snoop Filter operatively connected to the processor nodes and the I/O nodes to manage data information related to cache lines in one or more processor caches, said Snoop Filter comprising a cache array to store data information in a plurality of lines, and a Pseudo Least-Recently-Used (PLRU) replacement mechanism responsive to a processor transaction to identify a least-recently-used (LRU) line from the plurality of lines in the cache array for update to reflect lines that are replaced in one or more processor caches.