GB1208276A - Improvements in or relating to relating to data handling arrangements - Google Patents

Abstract

1,208,276. Data storage; computers. INTERNATIONAL COMPUTERS Ltd. 2 May, 1968 [3 May, 1967; 12 Aug., 1967], Nos. 20417/87 and 37132/67. Headings G4A and G4C. A data-handling arrangement, for accessing a data store including words arranged in pages arranged in segments, operates in accordance with whether page and segment portions of an address satisfy a predetermined requirement. In a multiprogrammed computer, a data store contains 64-word pages in 64-page segments which are in 64-segment zones. Besides data, the store contains a zone table pointer word, a one-page zone table, a 64-page segment table and a 4096-page page table. A data word can be accessed using a virtual address with zone segment, page and word portions by concatenating the zone table pointer word with the zone portion to address a word in the zone table, this word being concatenated with the segment portion to address a word in the segment table, this word being concateanated with the page portion to address a word in the page table, this word being concatenated with the word portion to address the required data word. However, the use made of the pointer word and the various tables is reduced using an associative store holding virtual address parts of the three forms: (1) zone, segment, page (2) ones, zone, segment (3) ones, ones, zone each form being accompanied by the corresponding table entry. The virtual address of the desired data word is inserted into a shift register and an associative match tried for with the above forms in turn until a match is found, the shift register being shifted to the right (with insertion of ones into the left end vacated positions) after associative interrogation for a given form before trying the next. If no match is found, the data word is obtained using the tables &c, as above. If a match is found, the corresponding table entry from the associative store is concatenated with the virtual address portion next to those used in the associative interrogation which gave match (e.g. the page portion if the matched entry was of form (2)) to address either the data word or a table entry. In the latter case, the word from the table is concatenated with the next portion from the virtual address to address either the data word or a table entry, and so on. Successive virtual address portions are presented for concatenation from the same portion of the shift register, by using repeated left shift, the left shift occurring in response to output of each table word from the data store, the first such word retrieved being also inserted into the associative store together with the corresponding portions of the virtual address from the shift register. As a modification, the associative store could also hold complete virtual addresses (on which a match is attempted first) and the corresponding data words.