International Business Machines Corporation

Julius Dwight Jones

Dale M Junod

Patrick M Gannon

Richard L Partridge

Thomas R Wright

This specification relates to performance of partial store operation in a hierarchical memory system which has a buffer store interposed between a processor interrogating the memory system and the main memory of the memory system. Such a partial store operation can be performed on a word of data in the main memory using the buffer store copy of that word of data. The copy of the word of data is read out of the buffer store into a register where it is modified to form a new word by replacing one or more but not all of the bytes in the word of data with bytes supplied by the processor. The new word is then placed in the main memory by performing a full store operation. The problem with performing a partial store operation in this manner is that the copy of the word of data in the buffer store may not be up-to-date. A technique is provided to eliminate the possibility of this old data being rewritten back into the main memory.

Technique for performing partial stores in store-thru memory

This specification describes an apparatus for determining if more than one of n lines are up at a given time. The apparatus includes means for encoding the n lines into m lines where n = 2.sup.m. Two encoding signals are generated; one, X.sub.0 X.sub.1 . . . X.sub.m, complement of the other, Z.sub.0 Z.sub.1 . . . Z.sub.m. These two signals are Ex OR'd in accordance with the formula (X.sub.0 Z.sub.0) .sup.. (X.sub.1 Z.sub.1) . . . (X.sub.m Z.sub.m). If more than one line is up, the resultant of the Ex OR operation is one. Otherwise the resultant is zero.

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Wappingers Falls, NY, United States of America

Julius Dwight Jones