Nec Corporation

Bull Hn Information Systems, Inc.

Zenith Data Systems Corporation

Packard Bell Nec

Michelle A Pence

Jeffrey S Somers

Thomas F Joyce

Jian-Kuo Shen

Chester M Nibby, Jr

Bruno DiPlacido, Jr

Thomas L Murray, Jr

James F Bertone

G Lewis Steiner

Martin Massucci

Marc Sanfacon

Lance J McNally

George J Barlow

William S Wu

Suresh K Marisetty

Norman J Rasmussen

Puthiya K Nizar

Raymond D Bowden, Iii

Marc E Sanfacon

Lance T McNally

Lewis G Steiner

Bruno Diplacido

Lance Mcnally

The invention is directed to a memory controller for use with memory having varying timing characteristics. In particular, the timing characteristics of the various memory devices are determined and used to generate timing signals commensurate with each particular memory device.

Symmetric multiprocessing system with unified environment and distributed system functions

A symmetric multiprocessing system with a unified environment and distributed system functions provides unified address space for all functional units in the system while distributing the execution of various system functions over the functional units of the system whereby each functional unit assumes responsibility for its own aspects of these operations. In addition, the system provides improved system bus operation for transfer of data from memory.

Symmetric multiprocessing system with unified environment and

Timing calculator means in a computer system are used to adaptively generate an appropriate access signal, to one of a plurality of memory types, based on first and second timing control values, wherein the first timing control value represents information specific to and limited to the start of a memory operation and wherein the second timing control value represents information representing other timing events. That is, the state machine of the present invention requires a distinct starting control value, separate from other timing values, for calculation of appropriate memory access parameters.

Adaptively generating timing signals for access to various memory

Memory retry logic to improve the resilience of system memory operations with respect to system errors or faults which prevent a memory read operation from being completed on a first attempt by allowing the memory to retry the operation once. The memory retry logic detects the occurrence of an improper response from the system element requesting a memory read operation when attempting to initiate the system bus operation for reading the data from memory to the requesting element and, if an improper response indicating that the requesting element is not accepting the bus operation request is detected, stores the memory operation request and the requested data and retries the data transmission on the next available bus cycle. If the memory receives an improper response of a specified type during a bus operation of a memory burst, the memory will terminate the operation and proceed to the next requested operation.

Method and apparatus for memory retry

A method and apparatus for resetting memory state when power is applied to the system. The memory has memory elements, a refresh clock and a refresh counter for counting refresh cycles and providing refresh signals to the memory elements, the memory elements and refresh means being connected from the power system and from a battery back-up means. A state detection means is connected from the refresh counter for detecting a change in state of the refresh counter to a state equivalent to the reset state of the refresh counter and asserting a state change signal. A means responsive to the state change signal and to the occurrence of the reset signal provides a memory controller reset signal, so that the memory controller reset signal occurs in synchronization with the change of state of the refresh counter to a state equivalent to the refresh counter reset state. The memory reset further includes a time-out counter means responsive to the assertion of the reset signal and to the refresh clock for counting refresh cycles in synchronization with the refresh counter. A time-out detection means is responsive to the time out counter means for providing a time out signal when the time-out counter has counted a refresh period plus one clock cycle and to the state change signal for providing the memory controller reset signal when the time-out counter has counted a refresh cycle plus one clock period and the state change signal has not been asserted.

Method and apparatus for resetting a memory upon power recovery

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Chelmsford, MA, United States of America

Michelle A Pence