A symmetric multi-processing system for processing exclusive read
requests. The system includes a plurality of cell boards, each of which
further includes at least one CPU and cache memory, with all of the cell
boards being connected to at least one crossbar switch. The read-latency
reducing system includes write-through cache memory on each of the cell
boards, a modified line list on each crossbar switch having a list of
cache lines that have been modified in the cache memory of each of the
cell boards, and a cache coherency directory on each crossbar switch for
recording the address, the status, and the location of each of the cache
lines in the system. The modified line list is accessed to obtain a copy
of a requested cache line for each of the exclusive read requests from
the cell boards not containing the requested cache line.