International Computers Limited

Nicholas Peter Holt

Peter L Desyllas

John Richard Eaton

Brian J Procter

Andrew J Knowles

Mark N Fullerton

Michael Fields

An authentication device consists of a hand-held unit having a receptacle for a smart card and an audio interface for communication with a telephone line. A challenge-and-response authentication procedure is performed between the smart card and a remote service. The device is dedicated solely to said authentication procedure and has no display.

Authentication device

A rotating memory system (e.g. a disk memory) in which a write request is allocated a physical block preferentially on the cylinder on which read/write heads are currently located. This reduces the amount of head movement and hence speeds up the access time. A block map is maintained to convert between the logical block numbers used by read and write requests and the physical block numbers which identify the physical locations of the blocks in the memory.

System and method for allocating a write request on the same cylinder as

A data processing apparatus, having a visible register map for associating physical registers with logical registers. Instructions involving register-to-register transfers are executed by altering the association between the physical registers and the logical registers, without actually transferring data between the registers, so as to avoid logically redundant operations and to take such instructions out of the critical path of execution.

Data processing apparatus with improved mechanism for executing

A data processing system has a scheduling unit for scheduling instructions from a number of instruction streams, and assigning those instructions to a number of execution units. A termination unit receives the results of the execution and informs the scheduling unit of which operands are available. The scheduling unit uses the operand availability information to control the scheduling of the instructions.

Data processing system for handling multiple independent data-driven

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.

Semaphore mechanism for a data processing system

A microprogram controlled data processing apparatus is described, in which each machine-level instruction is divided into a number of phases, and each phase is executed by a sequence of microinstructions. The machine-level instruction is decoded to produce a set of microprogram parameters, and in each phase of the instruction a sub-set of these parameters is selected, and broadcast over a parameter bus to individual decoders which decode the microinstructions, so as to qualify the effects of the microinstructions. The use of parameters in this way allows the same microprogram sequence to be used for several different instruction variants, and hence reduces the total size of the microprogram.

Microprogram control

Search apparatus is described for locating an item which satisfies a predetermined criterion e.g. an instruction ready for execution or a free block of data. The apparatus uses a tree structure where each terminal node represents one of the items and is set if that item satisfies the criterion. A non-terminal node is set if any of its subordinate nodes is set. In order to locate an item, a path is traced through the tree, starting at the root node and passing through a series of set nodes until a set terminal node is reached.

Search apparatus

Clearance arrangement for data storage apparatus. Data items D are entered into a store 10 together with a tag T equal to the current value of a counter 11. Data items are valid only while the counter 11 retains its current value. When it is desired to clear the store 10 the counter is incremented so that items with the previous tag value are rendered invalid. On some or all of such occasions a fraction of the store locations are also cleared by setting their tags to a null value. By the time the counter has completed a cycle all locations have been cleared in this way and cannot erroneously appear to contain valid data remaining from the previous cycle. The store is out of action to allow it to be cleared only for a relatively short time. Different tag counters may be used for different data types.

Data storage apparatus

Data processing apparatus includes a number of units connected by a bus over which each unit can send public write messages to all the other units in parallel. The units are connected in a loop by means of public write acceptance lines. Whenever a unit receives a public write message it sends an acceptance signal to the next unit in the loop. Each unit produces an error signal if it receives a public write message but does ot receive any corresponding acceptance signal, or if it receives an acceptance signal without having received a corresponding public write message. Thus, each unit checks its neighbors in the loop to ensure correct reception of the messages.

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Cheshire, United Kingdom

Nicholas Peter Holt