Stratus Technologies Bermuda Ltd.

Stratus Computer Systems, S.a.r.l.

Jeffrey S Somers

Simon P Graham

Mark Tetreault

Timothy Wegner

Steven Michael Haid

John W Edwards, Jr

Daniel J Lussier

Andrew Alden

Michael McLoughlin

Dan Lussier

John Edwards

Wen-Yi Huang

Nicholas Warchol

Laurent Fournie

Kurt Thaller

Tim Wegner

A system is provided for rapidly synchronizing two or more processing elements in a fault-tolerant computing system. Embodiments of this system allow for the rapid synchronization of two processing elements through partial copies of the contents of memory associate with each processing element.

Systems and methods for maintaining lock step operation

Methods and systems are provided by which a computer system, and in particular, a lockstep fault-tolerant computer system, may be split into a plurality of independently operational subsystems. Each subsystem may be examined, managed or upgraded by an administrator while the overall computer system continues to service end-users. Finally, the separate subsystems may be merged in an efficient fashion and fault-tolerant operation will resume upon the combined system.

Systems and methods for split mode operation of fault-tolerant computer systems

The present invention relates to a method and system for transferring portions of a memory block. A first data mover is configured with a first start address corresponding to a first portion of a source memory block. A second data mover is configured with a second start address corresponding to a second portion of the source memory block sized differently from the first portion. The first portion of the source memory block is transferred by the first data mover and the second portion of the source memory block is transferred by the second data mover.

Method and apparatus for efficiently moving portions of a memory block

A fault-tolerant computer system includes first and second central processing units (CPUs) producing essentially identical data output streams, a voter delay buffer having a first FIFO buffer and a second FIFO buffer, and an I/O module connected to the CPUs. The I/O module includes a comparator for bitwise comparing the CPU data output streams. The first CPU data output stream is transmitted to peripheral devices if both CPU outputs remain substantially identical. Otherwise, if the comparator indicates differences, queued first and second CPU data are routed to the first and second FIFOs respectively, and subsequent data are retained in respective CPU buffers. While the CPUs continue processing, ongoing diagnostic procedures attempt to identify one or the other of the CPUs as malfunctioning and the remaining CPU as correctly-functioning. If the resulting diagnosis is inconclusive, the CPU having the lower rate of error correction is identified as being correctly-functioning. In either case, the buffered output and the subsequently processed data output stream from the correctly-functioning CPU are thereafter transmitted to the peripheral devices.

Fault-tolerant computer system with voter delay buffer

A method and apparatus for maintaining clock phase alignment among system modules of a fault-tolerant computing system. In one embodiment, a low-frequency system reference clock signal is distributed to all system modules where it is multiplied to generate higher-frequency local clock signals. All local clock signals are then synchronized to the rising edge of the reference clock signal and the first rising edge in relation to a timing event is also identified.

Methods and apparatus for generating high-frequency clocks deterministically from a low-frequency system reference clock

A method and apparatus for controlling processor clock rates of a synchronous multi-processor system in response to an environmental condition of a processor. In one embodiment, a processor-reported an environmental condition is stored in a register and all processors are interrupted simultaneously. Upon interrupt, each processor reads the contents of the register and responds by adjusting its local clock rate synchronously with the other processors. In another embodiment, the processor's environmental status is polled by software control. Upon notification of an environmental condition, the software control notifies each processor to adjust its local clock rate synchronously with the other processors.

Methods and apparatus for clock management based on environmental conditions

The inventive system includes an I/O subsystem that controls the synchronization of an off-line CPU to an on-line CPU, such that much of the synchronization operation takes place essentially as a background task for the on-line CPU. The I/O subsystem requests that the on-line CPU provide certain register and memory state information to general purpose registers on an I/O board. The I/O subsystem then provides the register contents to general purpose registers on the off-line CPU board, and the off-line CPU uses the information to set the states of certain of its registers and memory. The I/O system further includes a DMA engine that, at a time set by the I/O subsystem, copies pages of memory from the on-line CPU to the off-line CPU. At the end of the synchronization operation, the off-line CPU is directed to write to a predetermined register on the I/O board. When the off-line CPU performs the write operation, it indicates that the off-line CPU is in a known state and ready to go on-line. The I/O subsystem then holds the off-line CPU in the known state by stalling the return of an acknowledgement of the write operation. When the on-line CPU later performs the same write operation, the on-line and the off-line CPUs are then in essentially the same state. The I/O processor may then reset the CPUs to ensure that the off-line CPU goes on line and starts a next operating cycle in lock-step with the reset on-line CPU. The system also dynamically selects a CPU output stream comparison method based on the number of CPUs on line at a given time.

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Northborough, MA, United States of America

Jeffrey S Somers