GB1371597A - Bubble domain memory system - Google Patents

Abstract

1371597 Magnetic storage arrangements INTERNATIONAL BUSINESS MACHINES CORP 16 Jan 1973 [1 May 1972] 2207/73 Heading H3B [Also in Division G4] In a cylindrical magnetic domain storage system, a plurality of operational storage units 1, 2 ... N, Fig. 1, and a spare storage unit are provided on a single magnetic sheet 10, the spare unit being arranged to replace a faulty operational unit detected during manufacture or operation. Each storage unit is basically the same as the unit 1 shown except for the internal organization of its write decoder WD. The system is controlled from a control circuit 16 which operates a bias field source 14 and a domain propagation field source 12, as well as controlling common operational circuitry for the units comprising a write driver 18, a decode driver 20, a sense current source 22 and a clear current source 24. Operation of the write driver causes a domain generator G1 to pass a domain to the write decoder WD1 in each of the units. The write decoders of the storage units 1, 2 ... N each consist of two path selectors SW, Fig. 2, controlled by the direction of currents I DA , I DB from the decode driver, the path selectors being arranged so that only a selected one of a group of four decoders can pass a domain to a storage propagation path 28 at any time, while the remaining decoders pass respective domains to domain annihilators A1a-A4a. Domains in path 28 pass to a read decoder RD where they are either returned to path 28 for recirculation or pass through an, e.g. magneto-resistive, sensor S to a clear means CL. A further operational choice at the clear means either recirculates the domains by way of path 38 or extends them to an annihilator A1b. The write decoder of the space storage unit differs in that it comprises four path selectors SW arranged so that domains from generator GS normally pass directly to annihilator ASa. By selectively opening switches SA1 or SA2 and SB1 or SB2, which may be transistors or fusible links, the spare storage unit may be matched to the character of any of the operational storage units it is required to replace. Details of the path selectors are shown in Fig. 3 (for type SW1) and Fig. 4 (for type SW2). In Fig. 3 a downward current I DA in strip 42, or the absence of current, causes a domain BD to pass along upper path 46, while an upward current diverts the domain to lower path 48. In Fig. 4 only a downward current will divert a domain to the lower path 52. Domain propagation is by the combination of a rotating in-plane field H and permalloy overlay T and I bars 40, 50. A test system is shown in Fig. 7 in which the various storage units are automatically monitored by test equipment 60. If a fault is detected in a unit the equipment selectively operates switch controls A and B which selectively open a switch in each of the groups SA1, SA2 and SB1, SB2, Fig. 2, to bring the spare storage unit into use.