Abstract: In a high speed memory subsystem differences in each memory device's minimum device read latency and differences in signal propagation time between the memory device and the memory controller can result in widely varying system read latencies. The present invention equalizes the system read latencies of every memory device in a high speed memory system by comparing the differences in system read latencies of each device and then operating each memory device with a device system read latency which causes every device to exhibit the same system read latency.

Abstract: An improved technique and associated apparatus for timing calibration of a logic device is provided. A calibration test pattern is transferred to a logic device first at a data rate slower than normal operating speed to ensure correct capture of the pattern at the device to be calibrated. Once the pattern is correctly captured and stored, the test pattern is transmitted to the logic device at the normal operating data rate to perform timing calibration. The improved technique and apparatus permits the use of any pattern of bits as a calibration test pattern, programmable by the user or using easily-interchangeable hardware.

Abstract: An interface device provided on a motherboard, or with a memory control chip set, translates between a controller, intended to communicate with a packet based memory system, and a non-packet based memory system. Communications from a memory controller, intended to directly communicate with a RAMBUS RDRAM memory system, are translated for a memory system which does not comprise RAMBUS RDRAM. The interface device, or integrated circuit, is not located with the memory system. That is, the memory modules do not include the interface circuit. Instead, the interface device is located with the processor motherboard, or with the controller/bridge integrated circuit chip set, such that it is electrically located between a controller and main memory sockets.

Abstract: An apparatus and method couples memory devices in a memory module to a memory hub on the module such that signals traveling from the hub to the devices have the same propagation time regardless of which device is involved. The hub receives memory signals from a controller over a high speed data link which the hub translates into electrical data, command and address signals. These signals are applied to the memory devices over busses having equivalent path lengths. The busses may also be used by the memory devices to apply data signals to the memory hub. Such data signals can be converted by the memory hub into memory signals and applied to the controller over the high speed data link. In one example, the memory hub is located in the center of the memory module.

Abstract: A dual-mode dual-data rate (DDR) synchronous dynamic random access memory (SDRAM)/synchronous graphic random access memory (SGRAM). An exemplary DDR SDRAM/SGRAM comprises a single memory device, which itself comprises a memory array including a quad-bank DRAM and a logic circuitry. The logic circuitry is coupled to the memory array and is configurable to operate the single memory device in a first mode and a second mode. The first mode may include a delayed lock loop (DLL) capability while the second mode may include a non-DLL capability.

Abstract: Additional clock-outs are included on DRAMs in a multiple Dual In-Line Module Memory (DIMM) system having DRAMs of different data widths. The additional clock-outs balance the loads seen by the DRAM clock-out and data-out, thereby reducing signal skew between the DRAM data and clock lines. Additionally, in a second embodiment, every other clock line in a series of DRAMs comprising a DIMM are left unconnected. The data from the non connected DRAMs is clocked using the clock line of its neighbor.

Abstract: In a high speed memory subsystem differences in each memory device's minimum device read latency and differences in signal propagation time between the memory device and the memory controller can result in widely varying system read latencies. The present invention equalizes the system read latencies of every memory device in a high speed memory system by comparing the differences in system read latencies of each device and then operating each memory device with a device system read latency which causes every device to exhibit the same system read latency.

Abstract: A method and apparatus for masking data written to a memory device that reduces the effective write cycle time of the memory device is disclosed. Firing of the column selects is pre-empted, thereby masking data to be written to a memory device. By pre-empting the column selects, the margin required for disabling a write driver can be eliminated, thereby reducing the effective write cycle. Additionally, data masking can be performed on a per-byte basis by associating independent column selects with each data byte on multi-byte wide devices, e.g., x16 or x32.

Abstract: A synchronous memory device and its method of operation which can be set to operate at a plurality of supported prefetch modes. The prefetch mode may be set by programming a portion of a mode register of the memory device or by setting one or more programmable elements. For read operations, the synchronous memory device internally reads data corresponding to the largest supported prefetch size, and outputs read data corresponding to the current mode. For write operations the synchronous memory accepts write data corresponding to the selected prefetch mode and writes the received data to the array. Data words corresponding to data not received are masked from writing via a write masking circuit.

Abstract: A dual-mode dual-data rate (DDR) synchronous dynamic random access memory (SDRAM)/synchronous graphic random access memory (SGRAM). An exemplary DDR SDRAM/SGRAM comprises a single memory device, which itself comprises a memory array and a logic circuitry. The logic circuitry is coupled to the memory array and is configurable to operate the single memory device in a first mode and a second mode. The first mode may include a delayed lock loop (DLL) capability while the second mode may include a non-DLL capability.

Abstract: A synchronous dynamic random access memory (“SDRAM”) operates with matching read and write latencies. To prevent data collision at the memory array, the SDRAM includes interim address and interim data registers that temporarily store write addresses and input data until an available interval is located where no read data or read addresses occupy the memory array. During the available interval, data is transferred from the interim data register to a location in the memory array identified by the address in the interim array register. In one embodiment, the SDRAM also includes address and compare logic to prevent reading incorrect data from an address to which the proper data has not yet been written. In another embodiment, a system controller monitors commands and addresses and inserts no operation commands to prevent such collision of data and addresses.

Abstract: An integrated circuit memory device is designed for high speed data access and for compatibility with existing memory systems. An address strobe signal is used to latch a first address. During a burst access cycle the address is incremented internal to the device with additional address strobe transitions. A new memory address is only required at the beginning of each burst access. Read/Write commands are issued once per burst access eliminating the need to toggle the Read/Write control line at the device cycle frequency. Transitions of the Read/Write control line during a burst access will terminate the burst access, reset the burst length counter and initialize the device for another burst access. The device is compatible with existing Extended Data Out DRAM device pinouts, Fast Page Mode and Extended Data Out Single In-Line Memory Module pinouts, and other memory circuit designs.

Abstract: A synchronous dynamic random access memory (“SDRAM”) operates with matching read and write latencies. To prevent data collision at the memory array, the SDRAM includes interim address and interim data registers that temporarily store write addresses and input data until an available interval is located where no read data or read addresses occupy the memory array. During the available interval, data is transferred from the interim data register to a location in the memory array identified by the address in the interim array register. In one embodiment, the SDRAM also includes address and compare logic to prevent reading incorrect data from an address to which the proper data has not yet been written. In another embodiment, a system controller monitors commands and addresses and inserts no operation commands to prevent such collision of data and addresses.

Abstract: A SLDRAM System is provided with a plurality of in-circuit, calibratable memory modules and a memory controller for issuing unicast and multicast command packets to the memory modules. Command packets are transmitted over a unidirectional command link that includes a complementary pair of command clock lines, a command FLAG line and a plurality of noncomplemented command bit lines. Each of the command clock lines, command bit lines and the FLAG line is a SLIO transmission line. Data transfer operations are carried out in response to the command packets over one or more bidirectional data links that each includes two complementary pairs of data clock lines, and a plurality of noncomplemented data bit lines. Each of the data clock lines and the data bit lines is a SLIO transmission line. Each SLIO transmission line is single-end terminated and preferably tapped into by way of stub resistors.

Abstract: A method and apparatus for performing a block-write to a memory device comprising at least one register, a data input port, at least one memory bank, and a hardware device to block-write data from the register to the memory device, including receiving a first portion of block-write data from a data bus during a first half of a clock cycle; then, producing a second portion of the block-write data, and block-writing the first and second portions of the block-write data from a write logic unit to the memory bank at a double data rate as determined by the clock cycle.

Abstract: A synchronous dynamic random access memory (“SDRAM”) operates with matching read and write latencies. To prevent data collision at the memory array, the SDRAM includes interim address and interim data registers that temporarily store write addresses and input data until an available interval is located where no read data or read addresses occupy the memory array. During the available interval, data is transferred from the interim data register to a location in the memory array identified by the address in the interim array register. In one embodiment, the SDRAM also includes address and compare logic to prevent reading incorrect data from an address to which the proper data has not yet been written. In another embodiment, a system controller monitors commands and addresses and inserts no operation commands to prevent such collision of data and addresses, using a bypass of the memory array.

Abstract: A synchronous dynamic random access memory (“SDRAM”) operates with matching read and write latencies. To prevent data collision at the memory array, the SDRAM includes interim address and interim data registers that temporarily store write addresses and input data until an available interval is located where no read data or read addresses occupy the memory array. During the available interval, data is transferred from the interim data register to a location in the memory array identified by the address in the interim array register. In one embodiment, the SDRAM also includes address and compare logic to prevent reading incorrect data from an address to which the proper data has not yet been written. In another embodiment, a system controller monitors commands and addresses and inserts no operation commands to prevent such collision of data and addresses.

Abstract: A method and apparatus is provided for selecting a memory device or a group of memory devices in a memory system using dedicated bank select signals in combination with encoded chip selection signals. A memory controller transmits bank select signals over bank select signal lines and encoded chip select signals on the command and address bus which are used to select an individual memory device or group of memory devices in a bank for an operation.

Abstract: A method and apparatus is provided for selecting a memory device or a group of memory devices in a memory system using dedicated bank select signals in combination with encoded chip selection signals. A memory controller transmits bank select signals over bank select signal lines and encoded chip select signals on the command and address bus which are used to select an individual memory device or group of memory devices in a bank for an operation.

Abstract: A method and apparatus for masking data written to a memory device that reduces the effective write cycle time of the memory device is disclosed. Firing of the column selects is pre-empted, thereby masking data to be written to a memory device. By pre-empting the column selects, the margin required for disabling a write driver can be eliminated, thereby reducing the effective write cycle. Additionally, data masking can be performed on a per-byte basis by associating independent column selects with each data byte on multi-byte wide devices, e.g., ×16 or ×32.