Electrical computers and digital processing systems: memory – Storage accessing and control – Hierarchical memories
Patent
1998-02-17
2000-08-08
An, Meng-Ai T.
Electrical computers and digital processing systems: memory
Storage accessing and control
Hierarchical memories
711142, 711146, 711121, G06F 1200
Patent
active
061015822
ABSTRACT:
Depending on a processor or instruction mode, a data cache block store (dcbst) or equivalent instruction is treated differently. A coherency maintenance mode for the instruction, in which the instruction is utilized to maintain coherency between bifurcated data and instruction caches, may be entered by setting bits in a processor register or by setting hint bits within the instruction. In the coherency maintenance mode, the instruction both pushes modified data to system memory and invalidates the cache entry in instruction caches. Subsequent instruction cache block invalidate (icbi) or equivalent instructions targeting the same cache location are no-oped when issued by a processor following a data cache block store or equivalent instruction executed in coherency maintenance mode. Execution of the data cache clock store instruction in coherency maintenance mode results in a novel system bus operation being initiated on the system bus. The bus operation directs other devices having bifurcated data and instruction caches to clean the specified cache entry in their data cache to at least the point of instruction/data cache coherency and invalidate the specified cache entry in their instruction cache. When repeatedly employed in sequence to write one or more pages of data to system memory, the mechanism for maintaining coherency saves processor cycles and reduces both address and data bus traffic.
REFERENCES:
patent: 5226144 (1993-07-01), Moriwaki et al.
patent: 5276848 (1994-01-01), Gallagher et al.
patent: 5822765 (1998-10-01), Boatright et al.
patent: 5909698 (1999-06-01), Arimilli et al.
Arimilli Ravi Kumar
Dodson John Steven
Lewis Jerry Don
An Meng-Ai T.
Emile Volel
International Business Machines - Corporation
Monestime Mackly
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