Abstract: A cache memory contains a number of RAMs. The RAMs are addressed by independent hashing functions, so as to access a set of locations, one in each RAM. If the required data item is resident in the addressed set, it is accessed. Otherwise, the least-recently used location in the set is selected for overwriting with data from main memory. The contents of the RAM location that is about to be overwritten are saved, and then used to access the memory again in order to address a further set of locations. If any of this further set of locations is less recently used than the saved contents, the saved contents are loaded back into that location.

Abstract: A computer system comprises a number of replicated units. At least two of the units include monitoring components for monitoring the status of the system. The monitoring components communicate with each other to exchange status information, so as to enable both of the monitoring components to form a combined view of the status of the system, based on information gathered by both of the monitoring components. This enables each monitoring component to locate faults more precisely, and thus enables more appropriate recovery action to be taken.

Abstract: A data processing system comprises a number of managed objects, such as processors, a file system, a communications facility, a power supply, database services, and databases. A number of composite managed objects are defined, each including a number of the managed objects and/or composite managed objects as members. The statuses of the managed objects are monitored, and the status of each composite managed object is set by aggregating the status of all the members of that composite managed object. By aggregating the status of objects in this way, the operator's view of the system is simplified, making the task of managing the system significantly easier. The aggregation is performed using a rules database holding information defining a set of rules for aggregating the status of the members of each managed object.

Abstract: A cable guide for a bundle of optic fibre cables, consists of a number of stackable plastic quadrants, clamped together to form a number of channels. The quadrants have radial ribs to grip the cables and to provide stress relief. The cables are held in the channels by a restraint.

Abstract: A data processing system includes a control computer which controls and monitors a cooling subsystem. The control computer has a non-volatile memory holding two status logs for recording stautus data and fault information. One of the logs is selected as the current log. If a fault condition is detected, the control computer writes fault information into the current log and then, if the other log is unlocked, locks the current log and selects the other log as the current log. In response to a "request locked log" command, the control computer transmits the contents of the locked log. In response to an "unlock" command, the control computer unlocks the locked log and then, if the other log contains fault information, locks that other log. The system thus provides an efficient mechanism for ensuring that the fault information is maintained, even through system powerdown.

Abstract: An optical bar code scanner has a laser for generating a coherent light beam, and a multifaceted rotatable mirror for scanning the beam. The scanned beam is reflected from at least three fixed mirrors. Two of these mirrors reflect the beam horizontally through a window in the scanner housing. Another mirror reflects the beam upwards, through a hologram, within the housing. The hologram converts the horizontal scanning pattern of this upwardly-reflected beam into a vertical scan pattern, directed horizontally through the window.

Abstract: A data switch interconnects a number of data processing nodes. The switch includes a number of port units for interfacing with the processing nodes, a number of multiplexing units for performing the switching, and a connection control unit. When a port unit wishes to initiate a connection, it sends a connection command over a command bus to all the multiplexing units and to the connection control unit, specifying a proposed data connection. Each multiplexing unit responds to the connection command by preparing the proposed data connection. At the same time, the connection control unit checks whether the proposed data connection is permissible. If it is permissible, the connection control unit then sends a GO signal to all the multiplexing units instructing them to complete the prepared connection.

Abstract: A design automation method for digital electronic circuits, including the steps of synthesizing a circuit including at least one logic tree, and then automatically partitioning the logic tree. The automatic partitioning process involves first identifying a set of driving bits for each of a set of points within the tree, ie the tree inputs that affect each of those points. Then, for each of those points, the partitioning process identifies a set of splittable input bits that can be isolated by insertion of a fence register at that point, and identifies which of those points are possible fence points, having more than one splittable input bit. Finally, the partitioning process selects a sub-set of the possible fence points, sufficient to reduce the number of inputs to the logic tree to a value less than a predetermined limit, and inserts fence registers at those points. In this way, the number of inputs to the logic tree can be made small enough (e.g. 17 or less) to allow exhaustive testing of the circuit.

Abstract: A distributed data processing system includes a distributed resource manager which detects dependencies between transactions caused by conflicting lock requests. A distributed transaction manager stores a wait-for graph with nodes representing transactions and edges connecting the nodes and representing dependencies between the transactions. Each edge is labelled with the identities of the lock requests that caused the dependency. The distributed transaction manager propagates probes through the wait-for graph, to detect cyclic dependencies, indicating deadlock. A deadlock message is then sent to the resource manager identifying a particular lock request as a victim for deletion to resolve the deadlock. Resilience to failure is achieved by duplicating between agents and servers, rather than by duplicating the servers. As a result, the number of messages between agents and servers in normal operation is not increased.

Abstract: A data processing system includes a first data processing environment including a plurality of application programs, and a second data processing environment including a plurality of software tools. A communication link interconnects the first and second environments. A tool agent in the first environment, provides an interface with each of the application programs. A tool server in the second environment, provides an interface with each of said tools.

Abstract: A data processing system is described, having a buffering mechanism for buffering data between two processes. The buffering mechanism includes a container table consisting of a number of data storage containers, an allocation list indicating which containers are free, and a communication list indicating which containers currently hold data waiting to be read by the recipient. The originator writes data into the first container indicated as free by the allocation list, removing that container from the allocation list and adding that container as the last container on the communication list. The recipient reads data from the first container indicated as in use by the communication list, removing that container from the communication list, and adding that container as the last free container on the allocation list.

Abstract: A configuration builder provides a common user interface for configuring a variety of different software components. The configuration builder consists of a number of component-specific builder modules and a generic user interface module. Each builder module contains templates defining user screens for inputting configuration information for a component, as well as validation rules and error messages. The configuration data for a component is obtained as set of tables, each containing records, and is then translated into the actual configuration file for use by the component.

Abstract: An electronic spreadsheet consists of an array of cells into which a user can enter formulas and values. The contents of the spreadsheet cells are translated into a query in a high-level logic language such as the Pure Logic Language (PLL). The query is then re-written according to the rules of the logic language, to produce an answer. The answer is then translated back into formulas and values which can be displayed on the spreadsheet. The system provides a number of facilities not available on conventional electronic spreadsheets: it provides the ability to give generalised answers containing formulas rather than simply numbers, and provides the ability to solve goal-seeking problems, working backwards from a desired result.

Abstract: A method of forming an electronic circuit assembly in which channels are formed in a surface of a circuit board e.g. by excimer laser drilling, and then filled with an optically transmissive resin material, to form an optical waveguide structure. A number of electronic devices are mounted on the circuit board, at least some of the devices including optical receiver and/or transmitter means for receiving/transmitting optical signals from/to the waveguide. An optical fibre is coupled to the waveguide.

Abstract: A method of constructing an electronic circuit assembly comprises forming a circuit board having first and second sets of circuit layers and an internal optically transmissive layer, sandwiched between the first and second sets of circuit layers. Holes are formed through the first set of circuit layers by excimer laser drilling, the holes extending as far as the optically transmissive layer without passing through that layer. Electronic devices are mounted on the circuit board over said holes, at least some of the devices including optical receiver and/or transmitter means for receiving/transmitting optical signals from/to the optically transmissive layer. An optical fibre is coupled to the optically transmissive layer. The optically transmissive layer thus acts as a bus interconnecting the devices.

Abstract: A disk drive module is described which externally has the physical and electrical appearance of a single standard 5.25 inch disk drive, but which internally contains five 2.5 inch disk drives and the electronics for operating them as resilient disk array. The disk drives are mounted on printed circuit boards which extend substantially the full length of the module. This provides a high data transfer rate and extremely high data reliability, and because the module has a standard form factor, it can be fitted to all types of system that can accommodate this form factor.

Abstract: In a computer system, a dialog management system (DMS) provides a bridge between a business application, based on a linear processing model, and a human-computer interface (HCI) based on an event-driven processing model. The DMS comprises a set of inventories, which are used to gather and receive application parameters and HCI information asynchronously, to allow sets of data items to be assembled.

Abstract: In a data processing system a number of processing nodes share resources. Access to the shared resources is controlled by semaphores, each node having a local copy of all the semaphores. Nodes may acquire ownership of semaphores. When a node requires a semaphore operation on a particular semaphore, a semaphore message is broadcast to all the nodes instructing them to perform the semaphore operation on their local copies of the semaphore. If the semaphore is unowned, the node must suspend the semaphore operation until the message returns, so as to ensure correct chronology for the semaphore operation. If, however, the semaphore owned by this node, the node can perform the semaphore operation without waiting for the message to return. This speeds up the semaphore mechanism. If the semaphore is owned by another node, that other node relinquishes ownership so that the semaphore operation can be performed.

Abstract: A data processing system includes at least one transaction processing application and a plurality of data managers which can be accessed by the transaction processing application. Each data manager is responsible for managing a separate data base. The system further includes a work-in-progress store and a work-in-progress store manager for managing the work-in-progress store. Whenever the transaction processing application instructs a data manager to perform an update, the data manager passes information concerning the update to the work-in-progress store manager which records this information in the work-in-progress store, and whenever the application completes a transaction, the data managers perform updates to their respective databases and the work-in-progress store manager is instructed to discard the contents of the work-in-progress store relating to this transaction.