Tandem Computers Incorporated

William T Fuller

Albert S Lui

Mark S Walker

Wing Ming Chan

Harald W Sammer

An apparatus and method for improving the input/output performance of a redundant storage array system. The present invention provides a 'special parity' cache within the controller for a redundant storage array system, and means for determining and caching a quantity known as the 'remaining redundancy row parity' (RRR-parity) block. The RRR-parity block is equal to the old parity block of a redundancy row XOR'd with an old data block being read from the same redundancy row. By caching RRR-parity blocks, Write-intensive storage unit operations can be reduced by up to three input/output accesses.

Redundant array parity caching system

An apparatus and method for monitoring the environment of remote components attached to a host processor by means of a standard interface bus having a limited number of address ports. The invention includes a host adapter incorporating a standard bus repeater component and an environment monitoring component. The environment monitoring component has a standard bus interface and is selectably coupled to the standard interface bus, and hence to a host processor. The host interface transceiver is coupled by means of a standard bus to the host processor, and is also selectably coupled to a drive interface transceiver by means of the standard bus. The drive interface transceiver is coupled by the standard bus to one or more storage devices. The host adapter is selectably switchable between two modes, such that either the drive interface transceiver is coupled through the host interface transceiver to the host processor, or the environment monitoring component is coupled to the host processor. The inventive system reduces the overhead of an environment monitoring system in terms of address ports on a standard bus having a limited number of address ports. In addition, the bus repeater component of the inventive system permits doubling the cable length limit imposed on certain standard buses, thereby permitting more remote location of one or more storage devices from a host processor.

Environment monitoring system for standard interface bus computer systems

A multiprocessing computer system with data storage array systems allowing for linear and orthogonal expansion of data storage capacity and bandwidth by means of a switching network coupled between the data storage array systems and the multiple processors. The switching network provides the ability for any CPU to be directly coupled to any data storage array. By using the switching network to couple multiple CPU's to multiple data storage array systems, the computer system can be configured to optimally match the I/O bandwidth of the data storage array systems to the I/O performance of the CPU's.

Linear and orthogonal expansion of array storage in multiprocessor

A special-purpose, microprogrammed digital subsystem sequences through stored lists of microinstructions to produce various control signals. In response to address signals provided by an address generator, the microinstructions are accessed in pairs: A primary microinstruction and a branch or target microinstruction. For the most part, only the primary microinstruction is decoded and executed. However, certain of the ones of primary microinstructions are of the type that require a decision to be made, and the microinstruction stream branches to one of two choices depending upon the outcome of the decision. The target microinstruction forms the first microinstruction of one of the available microinstruction branches, and, if this branch is taken, is executed in parallel with the branch to avoid time penalties. An additional aspect of the invention is that the address generator, which provides address signals to a memory that stores the microinstructions, is capable of functioning as a timer circuit.

Instruction sequencer branch mechanism

An apparatus determines the order of data communication between a plurality of peripheral devices that wish to do so and a central processor unit. Determination is made according to one of a number of selectable priority schedules. The apparatus is modifiable by programmed control so that certain of the peripheral devices can have their priorities reconfigured depending upon changing circumstances.

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San Jose, CA, United States of America

William T Fuller