System of coherent management of exchanges between two contiguous levels of a hierarchy of memories

Claim 1

In a hierarchal memory data processing system having a plurality of memory levels, each level being divided in separate data blocks, a page of each block of a higher speed level equalling a fraction of a page of each block of the next lower speed level, and each block of the lower speed level being arranged for exchanging information with blocks of the higher speed level, a system of coherent management of the exchanges between any two contiguous levels, one of higher speed than the other, comprising control processor means for managing said blocks at each level, said control processor means having at least one associated table containing status words for each block and means for updating said table responsive to each read-out and write-in request in said block and at each ejection of data from the block, wherein each control processor of a block of the lower speed level selectively, when receiving a read-out request from a block of the higher speed level, on consultation of its table, purges the blocks of the higher speed level of the fractions of the data addressed in the read-out request by repatriating the copies of such fractions existing in the blocks of the said plurality, accompanied by a decreasing one of the count in said table, of the fractions of a block in said higher level which has not yet been repatriated to the lower level, wherein each control processor of a block of the lower speed level selectively, when receiving a write-in request from a block of the higher speed level, on consultation of its table, updates the copies of fractions of the data addressed in said write-in request existing in the blocks of the higher speed level, and wherein: each table associated to a block of the lower speed level comprises as many entries as are pages in the block and, in each of its entries, comprises means to memorize the read-outs from the page corresponding to this entry and the identifications of the blocks of the higher speed level to which the read-outs send copies of fractions of the page, and, each table associated to a block of the higher speed level comprises as many entries as are pages in the block of the lower speed level with which it is in data exchange relation and, in each of its entries, comprises means to book an updated count of the copies of the fractions of the page of the block of the lower speed level corresponding to the entry and to concomitantly memorize an updated identification list of pages of the block of the higher speed level which contain such copies, and comprises means for signalling the passage to zero of each of the said counts to the respective blocks of the lower speed level, whereby each control processor of a block of the lower speed level is kept posted of the status of the copies of all fractions of data of its block within the blocks of the said plurality of the higher speed level.