Abstract: A system and method for providing concurrent column and row operations in a memory system is provided. The memory system includes a memory controller, a plurality of memory devices, and communication paths between the memory controller and the plurality of memory devices. The memory controller is coupled to each memory device through a communication path that provides a column chip select signal to the memory device and a communication path that provides a row chip select signal to the memory device. The dual chip select signals allow a column operation to be carried out in the memory device simultaneously with a row operation in the memory device.

Abstract: A mechanism for automatically detecting whether a selected type of cache memory is implemented within a cache memory element. The mechanism features a dedicated control line coupled between the cache memory element and a system controller. Logic circuitry is coupled to the control line to force the line to a first logic level in the event that the cache memory element has no connection to support the control line. However, if the cache memory element contains the selected type of cache memory, the logic circuitry is unable to for force the control line to go from a second logic level to the first logic level. After system reset, the system controller samples the voltage on the control line to determine whether the cache memory element is implemented with the selected type of cache memory.

Abstract: The present invention provides a system and method for providing reliable transmission in a buffered memory system. The system includes memory devices, a memory controller, data buffers, an address/command buffer, and a clock circuit. The memory controller sends data, address information, status information and command information, to the memory devices and receives data from the memory devices. The buffers interconnect the memory devices and the memory controller. The clock circuit is embedded in the addr/cmd buffer. The clock circuit takes an input clock and outputs an output clock to the data buffers and/or the memory devices to control clock-skew to the data buffers and/or the memory devices.

Abstract: A memory system includes a plurality of memory device ranks. A memory controller having a connection with the plurality of memory device ranks is adapted to obtain command information being issued to one of the plurality of memory device ranks. The memory controller is also adapted to generate a power weight value based on a command type from the command information. The memory controller increments a power count of the one of the plurality of memory device ranks by the power weight value generated. The memory controller then compares the power count of the one of the plurality of memory device ranks to a threshold value set for the one of the plurality of memory device ranks. If it is determined that the power count exceeds the threshold value, the memory controller is adapted to throttle the one of the plurality of memory device ranks.

Abstract: In a memory subsystem having a plurality of memory banks populated with up to a corresponding plurality of dynamic random access memory (DRAM) modules, the DRAM modules being of an extended data out type DRAM module or a page mode type DRAM module, ascertaining the type of DRAM module installed in populated ones of the plurality of memory banks. The DRAM type is determined by storing a predetermined value to a predetermined location in populated ones of the plurality of memory banks, and subsequently reading data from the predetermined location of populated ones of the plurality of memory banks using a page read control signal suitable for the extended data out type DRAM modules. If the data read corresponds to the predetermined value stored, an extended data out type DRAM module is identified.

Abstract: In a memory subsystem having a plurality of memory banks populated with up to a corresponding plurality of dynamic random access memory (DRAM) modules, the DRAM modules being of an extended data out type DRAM module or a page mode type DRAM module, ascertaining the type of DRAM module installed in populated ones of the plurality of memory banks. The DRAM type is determined by storing a predetermined value to a predetermined location in populated ones of the plurality of memory banks, and subsequently reading data from the predetermined location of populated ones of the plurality of memory banks using a page read control signal suitable for the extended data out type DRAM modules. If the data read corresponds to the predetermined value stored, an extended data out type DRAM module is identified.

Abstract: Methods and apparatus for a memory system using a branching point-to-point memory bus architecture are disclosed. In one embodiment, a primary memory controller maintains a point-to-point bus connection with one memory module and that memory module maintains a separate point-to-point bus connection with a second module. Data passing between the memory controller and the second memory module passes through a buffer circuit on the first memory module. For data received from the memory controller, the buffer circuit also passes that data up a module bus segment to a first bank of memory devices. That bank of memory devices maintains a second module bus segment with a second bank of memory devices. Data passing between the buffer circuit and the second bank of memory devices passes through a pass-through circuit on the first bank of memory devices. In this manner, a point-to-point memory bus architecture can be maintained even when a memory module contains more than one bank of memory devices.

Abstract: A method of handling memory read return data from different time domains includes determining a number of distinct memory device ranks. A time domain for each of the distinct memory device ranks is determined. A transaction is scheduled based on the time domain for each of the distinct memory device ranks so that at least one of data collisions and out-of-order data returns are prevented.

Abstract: A memory interface scheme reduces propagation delay by utilizing source-synchronous signaling to transmit address/command information to memory devices. A memory module in accordance with the present invention may include an address/command buffer that samples address/command information responsive to an address/command strobe signal and then passes the address/command information to a memory device on the module. A retiming circuit may be used to control the timing of read-return data from a memory device on the module.

Abstract: A computer system is disclosed with a host bridge that arbitrates access to a system resource from a CPU via a host bus and from a set of bus agents via a peripheral bus. A separate set of priority classes are provided to the CPU and to the bus agents and programmable timers are included to tune system resource allocation between the host and processor busses.

Abstract: Methods and apparatus for a memory system using a new memory module architecture are disclosed. In one embodiment, the memory module has two ranks of memory devices, each rank connected to a corresponding one of two 64-bit-wide data registers. The data registers connect to two 64-bit-wide ports of a 128:64 multiplexer/demultiplexer, and a 64-bit-wide data buffer connects to the opposite port of the multiplexer/demultiplexer. A controller synchronizes the operation of the data registers, the multiplexer/demultiplexer, and the data buffer.

Abstract: Methods and apparatus for a memory system using a branching point-to-point memory bus architecture are disclosed. In one embodiment, a primary memory controller maintains a point-to-point bus connection with one memory module and that memory module maintains a separate point-to-point bus connection with a second module. Data passing between the memory controller and the second memory module passes through a buffer circuit on the first memory module. For data received from the memory controller, the buffer circuit also passes that data up a module bus segment to a first bank of memory devices. That bank of memory devices maintains a second module bus segment with a second bank of memory devices. Data passing between the buffer circuit and the second bank of memory devices passes through a pass-through circuit on the first bank of memory devices. In this manner, a point-to-point memory bus architecture can be maintained even when a memory module contains more than one bank of memory devices.

Abstract: A computer system is disclosed with a host bridge that arbitrates access to a system resource from a CPU via a host bus and from a set of bus agents via a peripheral bus. A separate set of priority classes are provided to the CPU and to the bus agents and programmable timers are included to tune system resource allocation between the host and processor busses.

Abstract: An interface and method for a synchronous DRAM (syncDRAM) memory are provided that improve performance. The read operation in a syncDRAM is significantly sped up by eliminating the step of opening a new page of data in a SyncDRAM using a speculative read method. This provides the ability to open a page of information in the SyncDRAM with a command generator in response to a data request. Speculative read logic is also included to continue reading from the page with an invalid address until a second read request occurs. Thus, in the event that a subsequent read request occurs that requests data located on the same page as the prior request, the data can be indexed and read from a location on that page without having to first assert the SCS# and SCAS#. This frequently removes the step of opening a page from the read process and, over time, can significantly speed up the overall SyncDRAM reads in a computer system.

Abstract: A mechanism for automatically detecting whether a selected type of cache memory is implemented within a cache memory element. The mechanism features a dedicated control line coupled between the cache memory element and a system controller. Logic circuitry is coupled to the control line to force the line to a first logic level in the event that the cache memory element has no connection to support the control line. However, if the cache memory element contains the selected type of cache memory, the logic circuitry is unable to for force the control line to go from a second logic level to the first logic level. After system reset, the system controller samples the voltage on the control line to determine whether the cache memory element is implemented with the selected type of cache memory.

Abstract: A queue structure for transmitting a multiple-bit signal from a first sub-system operating in a first clocking domain in a computer system to a second sub-system operating in a second clocking domain in the computer system is disclosed. The queue structure comprises a queue data latch having a plurality of storage elements, wherein each of the plurality of storage elements can store the multiple-bit signal from the first sub-system. A load pointer is used for generating a first multiple-bit count indicating one of the plurality of storage element for storing the multiple-bit signal. A synchronization unit is coupled to the load pointer for receiving the first multiple-bit count. The synchronization unit outputs the multiple-bit count at the second sub-system when the multiple-bit signal is ready to be sampled in the second clocking domain.

Abstract: An arbitration circuit which controls arbitration for a resource by a first plurality of agents including a latency sensitive agent. The arbitration circuit comprises a mapping circuit and an arbiter. The mapping circuit is coupled to the first plurality of agents in order to receive a resource request signal from the latency sensitive agent and thereafter produce a plurality of request signals identical to the resource request signal. These request signals are input into at least a first and second I/O ports of the arbiter. The arbiter, which is coupled to the mapping circuit, including a second plurality of I/O ports and a second plurality of control ports each corresponding to one of the I/O ports. The arbiter is configured to arbitrate request signals input into the second plurality of I/O ports including the plurality of request signals, to monitor which I/O port was last activated, and to deactivate a control port associated with the I/O port thereby producing a control signal.

Abstract: A method of improving computer system performance during memory reads. Prior art computer systems experience a considerable time penalty during microprocessor reads from system memory. This time penalty is mitigated by the method of the present invention, wherein data is speculatively retrieved from system memory upon receipt of a microprocessor read request. A microprocessor initiates a read request which is decoded by a memory controller. Before the decoding has completed, the memory controller speculatively begins to retrieve data from the system memory device. Thus if the decode step determines that the requested data is in system memory, the time required to retrieve the data is decreased.