GB1536159A - Computer system and method of operating the same - Google Patents

Abstract

1536159 Address translation used in accessing data files PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 17 Dec 1975 [20 Dec 1974] 51625/75 Heading G4A A user address employed to access a user's data file stored in a secondary storage unit of a central data processor, the secondary storage unit including a first plurality of equal-capacity storage regions each including a second plurality of equal-capacity storage regions each including a third plurality of storage regions, is first converted to a logical address which is in turn processed by arithmetical means to provide a physical address including first, second and third physical address portions respectively relating to the first, second and third pluralities of storage regions. As described an 8-bit user address 157 and the two highest significance bits thereof access respective 12- and 4- bit words from stores 151, 152, these words being added at 160 to give the corresponding logical address 165. The secondary storage unit may be a magnetic disc store including 4 discs each having 20 or 10 sectors each of 50 or 100 tracks which respectively correspond to the first, second and third pluralities of storage regions. In this case the processing of the logical address by the arithmetical means consists of the division of the logical address by 50 or 100 at 184, using successive subtraction followed by shift, the quotient giving the track address and the remainder in turn being divided by 20 or 10 at 184, the final quotient giving the disc address and the final remainder the sector address. Alternatively, the secondary storage unit may be a magnetic domain store including 2 domain guide structures each having 3 domain loops each capable of storing 16 domains, which respectively correspond to the first, second and third pluralities of storage regions, Fig. 5 (not shown). In this case the processing of the logical address by the arithmetical means is performed by counter registers. It is stated that the secondary storage unit may alternatively consist of a plurality of shift registers or storage matrices.