Abstract: A computer system includes a plurality of memory modules that contain semiconductor memory, such as DIMMs. The system includes a host/data controller that utilizes an XOR engine to store data and parity information in a striped fashion on the plurality of memory modules to create a redundant array of industry standard DIMMs (RAID). To optimally run back to back cycles to the memory modules, a technique for providing de-rating parameters such that unnecessary latencies designed into the memory devices can be removed while the system is executing requests. By removing any unnecessary latency, cycle time and overall system performance can be improved.

Abstract: The control logic for a hot-pluggable memory cartridge for use in a redundant memory system. To implement a hot-pluggable memory cartridge in a redundant memory system, control logic to control the sequence of events for powering-up and powering-down a memory cartridge is provided.

Abstract: A technique for resynchronizing a memory system. More specifically, a technique for resynchronizing a plurality of memory segments in a redundant memory system after a hot-plug event. After a memory cartridge is hot-plugged into a system, the memory cartridge is synchronized with the operational memory cartridges such that the memory system can operate in lock step. A refresh counter in each memory cartridge is disabled to generate a first refresh request to the corresponding memory segments in the memory cartridge. After waiting a period of time to insure that regardless of what state each memory cartridge is in when the first refresh request is initiated all cycles have been completely executed, each refresh counter is re-enabled, thereby generating a second refresh request. The generation of the second refresh request to each of the memory segments provides synchronous operation of each of the memory cartridges.

Abstract: A computer system includes a plurality of memory modules that contain semiconductor memory, such as DIMMs. The system includes a host/data controller that utilizes an XOR engine to store data and parity information in a striped fashion on the plurality of memory modules to create a redundant array of industry standard DIMMs (RAID). The host/data controller also interleaves data on a plurality of channels associated with each of the plurality of memory modules. The system implements error interrupt control, ECC error reporting, cartridge error power down procedures in response to command errors, storage of error information in unused segments of each DIMM, hot-pug procedure indicator and remote tagging capabilities of memory cartridges and DIMMs.

Abstract: A computer system includes a plurality of memory modules that contain semiconductor memory, such as DIMMs. The system includes a host/data controller that utilizes an XOR engine to store data and parity information in a striped fashion on the plurality of memory modules to create a redundant array of industry standard DIMMs (RAID). The host/data controller also interleaves data on a plurality of channels associated with each of the plurality of memory modules. To optimize memory bandwidth and reduce memory latency, various techniques are implemented in the present RAID system. Present techniques include providing dual memory arbiters, sorting read cycles by chip select or bank address, providing programmable upper and lower boundary registers to facilitate programmable memory mapping, and striping and interleaving memory data to provide a burst length of one.

Abstract: A computer system includes an adaptive memory arbiter for prioritizing memory access requests, including a self-adjusting, programmable request-priority ranking system. The memory arbiter adapts during every arbitration cycle, reducing the priority of any request which wins memory arbitration. Thus, a memory request initially holding a low priority ranking may gradually advance in priority until that request wins memory arbitration. Such a scheme prevents lower-priority devices from becoming “memory-starved.” Because some types of memory requests (such as refresh requests and memory reads) inherently require faster memory access than other requests (such as memory writes), the adaptive memory arbiter additionally integrates a nonadjustable priority structure into the adaptive ranking system which guarantees faster service to the most urgent requests.

Abstract: A computer system includes a plurality of memory modules that contain semiconductor memory, such as DIMMs. The system includes a host/data controller that utilizes an XOR engine to store data and parity information in a striped fashion on the plurality of memory modules to create a redundant array of industry standard DIMMs (RAID). The host/data controller also interleaves data on a plurality of channels associated with each of the plurality of memory modules.

Abstract: A method of replacing a memory module in a computer system. Specifically, a method for replacing a memory module in a segment of a redundant memory system, without powering-down the memory system.

Abstract: A computer is provided having a bus interface unit coupled between a processor bus, a peripheral bus, and a memory bus. The bus interface unit includes a processor controller linked to the processor bus for controlling the transfer of cycles from the processor to the peripheral bus and memory bus. Those cycles are initially forwarded as a request, whereby the processor controller includes a memory request queue separate from a peripheral request queue. Requests from the memory and peripheral request queues can be de-queued concurrently to the memory and peripheral buses. This enhances throughput of read and write requests; however, proper ordering of data returned as a result of read requests and data transferred as a result of write requests must be ensured. An in-order queue is also present in the processor controller which records the order in which the requests are dispatched to the peripheral and memory buses from the peripheral and memory request queues.

Abstract: A method of adding memory capacity to a computer system. The computer system comprises a redundant memory system including a plurality of memory cartridges. By powering-down a memory cartridge, adding an additional memory module to the memory cartridge, and powering-up the memory cartridge for each memory cartridge in the system, the system can transition from a redundant mode of operation to a non-redundant mode of operation for each power-down, thus allowing the computer system to remain functional during the addition of the memory module. Alternatively, memory cartridges with higher memory capacity than those currently present in the computer system can be used to replace existing memory cartridges in the computer system, using the same techniques.

Abstract: The control logic for a hot-pluggable memory cartridge for use in a redundant memory system. To implement a hot-pluggable memory cartridge in a redundant memory system, control logic to control the sequence of events for powering-up and powering-down a memory cartridge is provided.

Abstract: A system and technique for correcting data errors in a memory device. More specifically, data errors in a memory device are corrected by scrubbing the corrupted memory device. Generally, a host controller delivers a READ command to a memory controller. The memory controller receives the request and retrieves the data from a memory sub-system. The data is delivered to the host controller. If an error is detected, a scrub command is induced through the memory controller to rewrite the corrected data through the memory sub-system. Once a scrub command is induced, an arbiter schedules the scrub in the queue. Because a significant amount of time can occur before initial read in the scrub write back to the memory, an additional controller may be used to compare all subsequent READ and WRITE commands to those scrubs scheduled in the queue.

Abstract: A computer system includes a plurality of memory modules that contain semiconductor memory, such as DIMMs. The system includes a host/data controller that utilizes an XOR engine to store data and parity information in a striped fashion on the plurality of memory modules to create a redundant array of industry standard DIMMs (RAID). The system supports DIMMs having X4 and X8 configurations. The system also transitions between various states, including a redundant state and a non-redundant state, to facilitate “hot-plug” capabilities utilizing its removable memory cartridges.

Abstract: A computer system includes an adaptive memory arbiter for prioritizing memory access requests, including a self-adjusting, programmable request-priority ranking system. The memory arbiter adapts during every arbitration cycle, reducing the priority of any request which wins memory arbitration. Thus, a memory request initially holding a low priority ranking may gradually advance in priority until that request wins memory arbitration. Such a scheme prevents lower-priority devices from becoming “memory-starved.” Because some types of memory requests (such as refresh requests and memory reads) inherently require faster memory access than other requests (such as memory writes), the adaptive memory arbiter additionally integrates a nonadjustable priority structure into the adaptive ranking system which guarantees faster service to the most urgent requests.

Abstract: A computer system includes a CPU and a memory device coupled by a bridge logic unit. CPU to memory write requests (including the data to be written) are temporarily stored in a queue in the bridge logic unit. The bridge logic unit preferably begins a write cycle to the memory device before all of the write data has been stored in the queue and available to the memory device. By beginning the memory cycle as early as possible, the total amount of time required to store all of the write data in the queue and then de-queue the data from the queue is reduced. Consequently, many CPU to memory write transactions are performed more efficiently and generally with less latency than previously possible.

Abstract: A computer is provided having a system interface unit coupled between main memory, a CPU bus, and a PCI bus and/or graphics bus. A hard drive is typically coupled to the PCI bus. The system interface unit is configured to perform a data integrity protocol. Also, all bus master devices (CPUs) on the processor bus may perform the same data integrity protocol. When a CPU requests read data from main memory, the bus interface unit forwards the read data and error information unmodified to the processor bus bypassing the data integrity logic within the system interface unit. However, the system interface unit may still perform the data integrity protocol in parallel with the requesting CPU so that the system interface unit may track errors and possibly notify the operating system or other error control software of any errors. In this manner processor read latency is improved without sacrificing data integrity. Furthermore, the system interface unit may still track errors on processor reads.

Abstract: A computer system includes an adaptive memory arbiter for prioritizing memory access requests, including a self-adjusting, programmable request-priority ranking system. The memory arbiter adapts during every arbitration cycle, reducing the priority of any request which wins memory arbitration. Thus, a memory request initially holding a low priority ranking may gradually advance in priority until that request wins memory arbitration. Such a scheme prevents lower-priority devices from becoming “memory-starved.” Because some types of memory requests (such as refresh requests and memory reads) inherently require faster memory access than other requests (such as memory writes), the adaptive memory arbiter additionally integrates a nonadjustable priority structure into the adaptive ranking system which guarantees faster service to the most urgent requests.

Abstract: A computer system includes a CPU, a memory device, two expansion buses, and a bridge logic unit coupling together the CPU, the memory device and the expansion buses. The CPU couples to the bridge logic unit via a CPU bus and the memory device couples to the bridge logic unit via a memory bus. The bridge logic unit generally routes bus cycle requests from one of the four buses to another of the buses while concurrently routing bus cycle requests to another pair of buses. The bridge logic unit preferably includes four interfaces, one each to the CPU, memory device and the two expansion buses. Each pair of interfaces are coupled by at least one queue; write requests are stored (or “posted”) in write queues and read data are stored in read queues.

Abstract: A computer is provided having a bus interface unit coupled between a CPU bus, a peripheral bus, and a memory bus. The bus interface unit includes a processor controller linked to the CPU bus for controlling the transfer of cycles from the CPU to the peripheral bus and memory bus. Those cycles can be arranged in order within the CPU bus pipeline. A subset of cycles destined for a peripheral bus can be stalled within a snoop phase associated with the CPU bus. Snoop stall can continue until a memory cycle is encountered upon the CPU bus pipeline within a phase prior to the snoop phase. Once the memory cycle progresses to the snoop phase, snoop stall can be discontinued and the previous, peripheral cycles can then be deferred and/or retried, allowing the memory cycle to be quickly dispatched through all phases of the CPU bus and onto the memory bus.

Abstract: A computer is provided having a bus interface unit coupled between a CPU bus, a peripheral bus (i.e., PCI bus and/or graphics bus), and a memory bus. The bus interface unit includes controllers linked to the respective buses, and a plurality of queues placed within address and data paths between the various controllers. The peripheral bus controller can decode a write cycle to memory, and the processor controller can thereafter request and be granted ownership of the CPU local bus. The address of the write cycle can then be snooped to determine if valid data exists within the CPU cache storage locations. If so, a writeback operation can occur. Ownership of the CPU bus is maintained by the bus interface unit during the snooping operation, as well as during writeback and the request of the memory bus by the peripheral-derived write cycle. It is not until ownership of the memory bus is granted by the memory arbiter that mastership is terminated by the bus interface unit.