International Business Machines Corporation

Dell Products Inc.

Advanced Micro Devices Corporation

John C Pescatore

Ronald J Cooper

Mario A Marsico

Paul D Sullivan

Michael R Marr

Gilbert S Burrus, Jr

David Brian Ruth

Randall Clay Itskin

Richard Colbert Matlack, Jr

Robert L Smith, Jr

A system and method is disclosed for detecting errors in memory. A memory subsystem that includes a set of parallel memory channels is disclosed. Data is saved such that a duplicate copy of data is saved to the opposite memory channel according to a horizontal mirroring scheme or a vertical mirroring scheme. A cyclic redundancy code is generated on the basis of the data bits and address bits. The generated cyclic redundancy code and a copy of the cyclic redundancy code are saved to the memory channels according to a horizontal mirroring scheme or a vertical mirroring scheme.

System and method for error detection in a redundant memory system

A method of accessing a memory includes accessing multiple ECC words via a single memory channel. Portions of each ECC word are retrieved from different memory ranks, so that a failure in a memory device at one memory rank is less likely to result in uncorrectable errors in the data segment. By accessing the data segments via a single memory channel, rather than multiple memory channels, the single memory channel can be accessed independently, providing for lower cost memory modules, higher memory bandwidth, and lower power dissipation.

Data error correction device and methods thereof

An information handling system having a plurality of modular servers and input-output (I/O) modules use virtual bridge switches to couple any of the plurality of modular servers to any of the I/O modules. This allows the modular servers to have the I/O connectivity dictated by the computing environment rather than having a fixed I/O assignment. The modular servers and I/O modules may be coupled together through serial I/O interfaces. Input and output buffers may be used to manage data flow traffic and multiplexers may be used to steer data to the appropriate input and output buffers. Control logic may be used to control the multiplexers and a programmable I/O mapping table may be used to describe which modular servers are coupled to which I/O modules.

Multi-host virtual bridge input-output resource switch

A computer system having a cache for providing data to the system's processing unit(s), wherein the cache controller selectively aborts speculative accesses to its data array. The cache initiates a transfer of data by speculatively transmitting an associated address to the data array, and the data transfer is aborted in response to an intervening determination that the data is to be provided by another source, e.g., by the system memory device (a cache miss) or, in a multi-processor computer wherein the cache is an L3 cache supporting several processing units, by another processing unit which holds the data in a modified state. The data array is arranged in rows and columns, and accessed using a row address strobe (RAS) signal and a column address strobe (CAS) signal. The cache initiates the data transfer by driving a RAS signal associated with the address, and the data transfer is aborted prior to driving a CAS signal associated with the address. The cache registers a state for a memory bank associated with the address, indicating that the memory bank requires a precharge, and later sends a precharge command to the memory bank. By aborting unnecessary data transfers, the L3 data bus is freed up to allow successful speculative access of other cache lines.

SDRAM L3 cache using speculative loads with command aborts to lower latency

Apparatus for and methods of detecting an error in multiple state lock step operated circuits. Signatures representing internal states of each circuit are conveyed in daisy chain format to connect successive circuits. Local comparisons between the received signatures and those representing previous internal states are used to detect mismatches between states. Signals indicating the detection of a mismatch appear on a commonly connected error line. Scanned comparison of the circuits to determine those having detected a mismatch allows the error source to be identified.

Validating the synchronization of lock step operated circuits

A communications concentrator and message multiplexer featuring direct access from the communications adapters to main memory via direct memory access means which eliminates the usual scanner or polling facility in a concentrator or multiplexer is described. A control microprocessor manages the allocation of memory, the conversion of message protocols and the servicing of interrupts to a plurality of port interface adapter microprocessors. The interface adapter microprocessors directly set up and control the DMA operation instead of having the DMA operation controlled by the control processor. One of the port adapters serves as a service adapter over a dedicated interface allowing a remote disgnostician access to internal registers in the control processor system, access to a dedicated read only storage for servicing, and logical interface to the main control processor for the purpose of entering instructions and directing functional operations to test each component of the system.

Scannerless message concentrator and communications multiplexer

Bus interconnection between the system busses of a multi-port communications controller and the busses of one or more multi-port adapters is facilitated with a new architecture for providing an interconnection controller. A programmably adjustable adapter and port interface controller is combined via a scannerless communications controller with a bus interconnection control logic that handles both DMA and interrupt mode data transfers for a large number of channels. The invention provides an improved apparatus and method for transferring data to or from numerous communication channel devices within a processor based communications system in such a manner that the optimum mode of data transfer may be individually programmed for each channel as system environment conditions demand.

Multiple port service expansion adapter for a communications controller

A multi-port communications controller and variable protocol adapter is described. The adapter utilizes a user programmable pluggable programming cartridge for defining individual communications port data service characteristics. The port data service characteristics are interpreted by a microprocessor which manages the interchange from port to port and to or from memory or a host system. Direct memory access or interrupt driven memory access modes of operation are individually selectable for each individual in bound and out bound communications channel. The communications protocols employed at each port may be of any standard type with the microprocessor in the adapter making the appropriate conversion. Communication speeds can be automatically recognized and matched for each port also. An arbitration processor for both DMA and interrupt driven data transfer services is included as the heart of the communications adapter design to provide the capability of individualized control over each in bound and out bound channel's mode of data transfer service for the optimum mode of operation for each port and type of data service required.

Multiple port communications adapter apparatus

Both DMA access and character interrupt driven access modes of service are provided to multiple communication ports by an integrated arbitration DMA/interrupt controller utilizing its own resident randomly accessible memory. Pipelined logic control architecture for handling service mode adaptations for each individual port and for managing memory accesses to main system memory enables the use of the random access memory with its inherent time delays in a manner that virtually eliminates the effect of any time delay in overall memory access throughput.

Multiple port integrated DMA and interrupt controller and arbitrator

In an arbitration apparatus and technique, the request lines from a plurality of potential requestors serve both as interrupt and DMA bus request signal lines to an arbitration device. The arbitration device selects among contending requestors on a priority basis and generates a grant signal interpreted by the requesting devices either as an interrupt grant or a bus grant depending upon whether or not an interrupt acknowledge signal is received. This effectively multiplexes the grant request lines from a plurality of requestors to greatly reduce interconnection complexity and cost. A single interrupt grant/bus grant multi-wire signal cable connects from the arbitration device to the individual requestors. A grant will appear on a single line thereof connected to an individual requestor that has been granted either an interrupt or access to the bus. Interrupt requests from the requestors are ORed together and simultaneously presented to a central controlling microprocessor. The arbitration device determines which requestor will be granted access and, under control of the central control microprocessor, the arbitrator gates an interrupt grant or a DMA grant signal to the device selected by the arbitration mechanism. The dual usage of the grant and request lines by the arbitration device represents a multiplexing feature to further reduce interconnections.

Multiplexed interrupt/DMA request arbitration apparatus and method

A multiprocessor array is described in which a central controlling microprocessor interfaces over commonly connected address and data busses to a plurality of peripheral microprocessors. A memory mapped I/O interface controls access to and from the busses for mutual receipt and exchange of signals between the processors and mutual exchange and receipt of data among the processors. The individual processors are selectively isolatable by a plurality of three state switch means connected between each processor and the interconnecting data and address busses. Error detection and control logic is connected via control lines to the individual processors and responsive to an error indication thereof, activates a multipoint error signal to all said microprocessors over a control line, which signal is interpreted by the processor then controlling said busses as a signal to deactivate its operation and as a signal at said control microprocessor to invoke an interrupt for analyzing the causes of said error. The control microprocessor can issue memory mapped I/O instructions to the individual three state selective isolation means and/or to any of the I/O microprocessors to respectively isolate the processors from said busses or to control said processors in an error analysis routine. The apparatus further includes a machine check register and a bus master register associated with said control microprocessor which registers can be written in by said control microprocessor and read from only by one of said I/O microprocessors.

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Durham, NC, United States of America

John C Pescatore