Abstract: A circuit arrangement, method and apparatus utilize communication links that are selectively configurable to operate in both unidirectional and bidirectional modes to communicate data between multiple nodes that are interconnected to one another in a daisy chain configuration. As a result, in many instances communications may be maintained with nodes located both before and after a discontinuity in a daisy chain configuration.

Abstract: A diagnostic interface architecture for a memory device supports in one aspect one or more dynamically reconfigurable functional interconnects normally utilized in connection with reading data from the memory device and/or writing data to the memory device. The dynamically reconfigurable functional interconnects are capable of being configured to operate in either functional or diagnostic modes, whereby in the diagnostic mode, such interconnects may be used to communicate diagnostic information to support one or more diagnostic operations. The diagnostic interface architecture may also support multiple diagnostic interfaces in a given memory device, with at least one such diagnostic interface being capable of being selectively enabled in response to a failure in another diagnostic interface.

Abstract: A diagnostic interface architecture for a memory device supports in one aspect one or more dynamically reconfigurable functional interconnects normally utilized in connection with reading data from the memory device and/or writing data to the memory device. The dynamically reconfigurable functional interconnects are capable of being configured to operate in either functional or diagnostic modes, whereby in the diagnostic mode, such interconnects may be used to communicate diagnostic information to support one or more diagnostic operations. The diagnostic interface architecture may also support multiple diagnostic interfaces in a given memory device, with at least one such diagnostic interface being capable of being selectively enabled in response to a failure in another diagnostic interface.

Abstract: A diagnostic interface architecture for a memory device supports in one aspect one or more dynamically reconfigurable functional interconnects normally utilized in connection with reading data from the memory device and/or writing data to the memory device. The dynamically reconfigurable functional interconnects are capable of being configured to operate in either functional or diagnostic modes, whereby in the diagnostic mode, such interconnects may be used to communicate diagnostic information to support one or more diagnostic operations. The diagnostic interface architecture may also support multiple diagnostic interfaces in a given memory device, with at least one such diagnostic interface being capable of being selectively enabled in response to a failure in another diagnostic interface.

Abstract: A circuit arrangement, method and apparatus utilize communication links that are selectively configurable to operate in both unidirectional and bidirectional modes to communicate data between multiple nodes that are interconnected to one another in a daisy chain configuration. As a result, in many instances communications may be maintained with nodes located both before and after a discontinuity in a daisy chain configuration.

Abstract: A high speed computer processor system has a high speed interface for a graphics processor. A preferred embodiment combines a PowerPC microprocessor called the Giga-Processor Ultralite (GPUL) 110 from International Business Machines Corporation (IBM) with a high speed interface on a multi-chip module.

Abstract: A method and apparatus is provided which dynamically alters SDRAM memory interface timings to provide minimum read access latencies for different types of memory accesses in a memory subsystem of a computer system. The dynamic alteration of the SDRAM memory interface timings is based on workload and is determined with information from the memory controller read queue.

Abstract: A circuit arrangement and method are used in connection with a data latch that is coupled to a data source over a source synchronous communications interface to disable the data latch from latching data whenever the data source is not driving the source synchronous data strobe signal. As such, when the data source is not driving the source synchronous data strobe signal, undesired and/or inadvertent latching by the data latch can be avoided. Moreover, in implementations where a data strobe signal line is bidirectional, and capable of being driven either by the data source or by another circuit used to access the data source (e.g., a memory controller), disabling data latching as described herein can minimize the risk of driver damage resulting from conflicting attempts to drive the data strobe signal line at both ends.

Abstract: An improved computer memory subsystem determines the most efficient memory command to execute. The physical location and any address dependency of each incoming memory command to a memory controller is ascertained and that information accompanies the command for categorization into types of command. For each type of memory command, there exists a command FIFO and associated logic in which a programmable number of the memory commands are selected for comparison with each other, with the memory command currently executing, and with the memory command previously chosen for execution. The memory command having the least memory cycle performance penalty is selected for execution unless that memory command has an address dependency. If more than one memory command of that type has the least memory cycle performance penalty, then the oldest is selected for execution.

Abstract: A programmable compensated delay for a double data rate (DDR) synchronous dynamic random access memory (SDRAM) interface is provided. A programmable compensated delay apparatus includes a reference delay calibration circuit for providing a measured number of delay elements in one cycle. A programmable delay register provides a desired delay value. A conversion logic is coupled to the reference delay calibration circuit and the programmable delay register for receiving both the measured number of delay elements in one cycle and the desired delay value. The conversion logic provides a number of required delay elements. A delay circuit is coupled to the conversion logic for receiving the number of required delay elements and providing the desired delay. A SDRAM control logic provides a refresh start signal to the reference delay calibration circuit for updating the delay circuit during each DRAM refresh. The DQS clock strobe on the DDR SDRAM is applied to the delay circuit and is delayed by the desired delay.

Abstract: A method and apparatus is provided which dynamically alters SDRAM memory interface timings to provide minimum read access latencies for different types of memory accesses in a memory subsystem of a computer system. The dynamic alteration of the SDRAM memory interface timings is based on workload and is determined with information from the memory controller read queue.

Abstract: A circuit arrangement and method are used in connection with a data latch that is coupled to a data source over a source synchronous communications interface to disable the data latch from latching data whenever the data source is not driving the source synchronous data strobe signal. As such, when the data source is not driving the source synchronous data strobe signal, undesired and/or inadvertent latching by the data latch can be avoided. Moreover, in implementations where a data strobe signal line is bidirectional, and capable of being driven either by the data source or by another circuit used to access the data source (e.g., a memory controller), disabling data latching as described herein can minimize the risk of driver damage resulting from conflicting attempts to drive the data strobe signal line at both ends.

Abstract: A circuit arrangement and method are used in connection with a data latch that is coupled to a data source over a source synchronous communications interface to disable the data latch from latching data whenever the data source is not driving the source synchronous data strobe signal. As such, when the data source is not driving the source synchronous data strobe signal, undesired and/or inadvertent latching by the data latch can be avoided. Moreover, in implementations where a data strobe signal line is bidirectional, and capable of being driven either by the data source or by another circuit used to access the data source (e.g., a memory controller), disabling data latching as described herein can minimize the risk of driver damage resulting from conflicting attempts to drive the data strobe signal line at both ends.

Abstract: A method and system for arbitrating data transfers between devices connected via electronically isolated buses at a switch. In accordance with the method and system of the present invention, multiple arbitration controllers are interposed between devices and a switch to which the devices are connected, wherein each of the multiple arbitration controllers are effective to select a data transfer operation and detect collisions between said selected data transfer operations. The switch is enabled for any selected data transfer operations between which collisions are not detected. The switch is also enabled for only one of the selected data transfer operations between which collisions are detected. Any selected data transfer operations for which the switch is not enabled are deferred.

Abstract: An internal processor/memory bus contains an address portion for transmitting addresses and commands, having a series of hierarchical uni-directional links between processors and local repeaters (ARPs), and between the ARPs and a central repeater (ASW). A command propagates from a requesting device to its local ARP, to the ASW. From the ASW, the command is broadcast to all devices on the bus by transmitting to all ARPs or directly attached memory, and from the ARPs to the devices. Preferably, the ASW globally arbitrates the address bus, and all commands propagate at pre-defined clock cycles through the bus. Preferably, each device on the bus independently signals a response via a separate response link running directly to a global collector, which collects all responses and broadcasts a single system-wide response back to the devices.

Abstract: A processor-memory bus comprises a command portion for transmitting addresses and commands, having a unidirectional input portion for transmitting commands to a central repeater unit, and a unidirectional broadcast portion for broadcasting commands from the repeater. The input portion comprises a plurality of links running from different devices, wherein each link is less than the full width of the broadcast bus portion. A command is transmitted over the input portion in a plurality of bus cycles, and broadcast over the broadcast portion in a single bus cycle. Since multiple input links connect to the central command repeater, it is possible to keep the broadcast bus full notwithstanding the fact that multiple bus cycles are required to transmit an individual command on the input portion. Preferably, the links are arranged hierarchically, from processors to local repeaters, from local repeaters to the central repeater, and back again.

Abstract: A shared bus non-sequential data ordering method and apparatus are provided. A maximum bus width value and a minimum transfer value are identified. A minimum number of sub-transfers is identified responsive to the identified maximum bus width value and the minimum transfer value. A bus unit having a maximum number of chips to receive and/or send data receives data in a predefined order during multiple sub-transfers. During each data sub-transfer, a corresponding predefined word is transferred to each chip of the bus unit.

Abstract: A method and apparatus for routing data between bus devices, where each bus device is connected to a centralized switch via a point-to-point bus connection. The plurality of point-to-point bus connections collectively form a system bus. After a command is issued on the system bus, each bus device responds to the issued command by transmitting an address status response to a response combining logic module. The response combining logic module identifies which of the bus devices responded with a positive acknowledgment to the issued command, then forwards a device identifier of the bus device responding with the positive acknowledgment to the switch. The switch uses the device identifier returned via the response combining logic to route the data transfer associated with the issued command.

Abstract: An apparatus, program product and method initialize a redundant memory device by delaying the switchover of non-initialization fetch operations from a failed memory device to the redundant memory device until after initialization of the redundant memory device is complete. Consequently, during initialization, the non-initialization fetch operations are directed to the failed memory device, while non-initialization store operations are directed to the redundant device.

Abstract: A processor-memory bus comprises a command portion for transmitting addresses and commands, having a unidirectional input portion for transmitting commands to a central repeater unit, and a unidirectional broadcast portion for broadcasting commands from the repeater. The input portion comprises a plurality of links running from different devices, wherein each link is less than the full width of the broadcast bus portion. A command is transmitted over the input portion in a plurality of bus cycles, and broadcast over the broadcast portion in a single bus cycle. Since multiple input links connect to the central command repeater, it is possible to keep the broadcast bus full notwithstanding the fact that multiple bus cycles are required to transmit an individual command on the input portion. Preferably, the links are arranged hierarchically, from processors to local repeaters, from local repeaters to the central repeater, and back again.