Abstract: A memory module includes several memory devices coupled to a memory hub. The memory hub includes several link interfaces coupled to respective processors, several memory controller coupled to respective memory devices, a cross-bar switch coupling any of the link interfaces to any of the memory controllers, a write buffer and read cache for each memory device and a read synchronization module. The read synchronization module includes a write pointer, a read pointer and a buffer. The write pointer is incremented in response to the receipt of read data. The read pointer increments in response to coupling of the read data from the memory hub. A comparator compares the read pointer an the write pointer, and the comparison is used to adjust the memory timing.

Abstract: A memory module includes several memory devices coupled to a memory hub. The memory hub includes several link interfaces coupled to respective processors, several memory controller coupled to respective memory devices, a cross-bar switch coupling any of the link interfaces to any of the memory controllers, a write buffer and read cache for each memory device and a read synchronization module. The read synchronization module includes a write pointer, a read pointer and a buffer. The write pointer is incremented in response to the receipt of read data. The read pointer increments in response to coupling of the read data from the memory hub. A comparator compares the read pointer an the write pointer, and the comparison is used to adjust the memory timing.

Abstract: A memory module includes several memory devices coupled to a memory hub. The memory hub includes several link interfaces coupled to respective processors, several memory controller coupled to respective memory devices, a cross-bar switch coupling any of the link interfaces to any of the memory controllers, a write buffer and read cache for each memory device and a read synchronization module. The read synchronization module includes a write pointer, a read pointer and a buffer. The write pointer is incremented in response to the receipt of read data. The read pointer increments in response to coupling of the read data from the memory hub. A comparator compares the read pointer an the write pointer, and the comparison is used to adjust the memory timing.

Abstract: An integrated circuit load board includes a substrate on which a plurality of integrated circuit sockets and an integrated test circuit are mounted. The integrated test circuit includes circuitry for testing the timing margins of memory devices by determining the relative timing between read data and data strobe signals applied to a memory device. The relative timing between the read data and data strobe signals is determined by using a delay line to delay the data strobe signal over a range of delays, and determining a final delay that causes the transitions of the delayed data strobe signal to coincide with the transitions of the read data signals. The time corresponding to the final delay is then determined by using a phase interpolator to generate a range of phase offset signals having known delay times until a phase offset signal has the same delay as the final delay.

Abstract: A memory module includes several memory devices coupled to a memory hub. The memory hub includes several link interfaces coupled to respective processors, several memory controller coupled to respective memory devices, a cross-bar switch coupling any of the link interfaces to any of the memory controllers, a write buffer and read cache for each memory device and a read synchronization module. The read synchronization module includes a write pointer, a read pointer and a buffer. The write pointer is incremented in response to the receipt of read data. The read pointer increments in response to coupling of the read data from the memory hub. A comparator compares the read pointer an the write pointer, and the comparison is used to adjust the memory timing.

Abstract: A memory module includes a memory hub that couples signals to memory devices mounted on opposite first and second surfaces of a memory module substrate. The memory devices are mounted in mirrored configuration with mirrored terminals of memory devices on opposite surfaces being interconnected. A memory hub mounted on each module alters the configuration of address and/or command signals coupled to the memory devices depending upon whether the memory devices on the first surface of the substrate or the memory devices on the second surface of the substrate are being accessed. Alternatively, the configuration of the address and/or command signals coupled to mirrored memory devices may be altered by a register mounted on the substrate that is coupled to the memory devices or by a memory controller coupled directly to memory devices on one or more memory modules.

Abstract: Write strobe preamble/postamble test circuitry includes a test signal generator generating first and second digital signals. Also included are a pair of phase interpolators for varying the transition times of respective transmitter clock signals. When enabled, a transmitter uses the transmitter clock signals to transmit a write data strobe signal corresponding to the first and second digital signals to memory devices being tested. The transmitter is enabled by an enable signal generated by a third phase interpolator. By varying the timing of the enable signal, the third phase interpolator can vary the duration of preambles and postambles of respective write data strobe signals.

Abstract: An integrated circuit load board includes a substrate on which a plurality of integrated circuit sockets and an integrated test circuit are mounted. The integrated test circuit includes circuitry for testing the timing margins of memory devices by determining the relative timing between read data and data strobe signals applied to a memory device. The relative timing between the read data and data strobe signals is determined by using a delay line to delay the data strobe signal over a range of delays, and determining a final delay that causes the transitions of the delayed data strobe signal to coincide with the transitions of the read data signals. The time corresponding to the final delay is then determined by using a phase interpolator to generate a range of phase offset signals having known delay times until a phase offset signal has the same delay as the final delay.

Abstract: The timing of output signals can be controlled by coupling a digital signal through a signal distribution tree having a plurality of branches extending from an input node to respective clock inputs of a plurality of latches. A phase interpolator is included in a signal path common to all of the branches, and a respective delay line is included in each of the branches. Each of the latches couples a signal applied to its data input to an output terminal responsive to a transition of the digital signal applied to its clock input. The delay lines are adjusted so that the latches are simultaneously clocked. The delay of the phase interpolator is adjusted so that the signals are coupled to the output terminals of the latches with a predetermined timing relationship relative to signals coupled to output terminals of a second signal distribution tree.

Abstract: A testing system includes a phase interpolator receiving a clock signal. An output of the phase interpolator is coupled to both a first signal distribution tree that includes a first delay line in each of its branches and a second signal distribution tree that includes a second delay line in each of its branches, thereby producing respective first and second delayed clock signals. A test signal generator generates a plurality of test signals that may simulate memory command or address signal. A multiplexer couples the test signals to first and second inputs of a transmitter in a normal test mode but to only the first input in a special test mode. The transmitter outputs the signal applied to its first input responsive to the first delayed clock signal and it outputs the signal applied to its second input responsive to the second delayed clock signal.

Abstract: Circuits and methods are provided that alleviate overloading of the command address bus and limit decreases in command address bus bandwidth to allow increased numbers of memory modules to be included in a computer system. A plurality of switches is coupled between the command address bus (which is coupled to the memory controller) and a respective plurality of memory modules. Each switch provides command address bus data only to its respective memory module. Preferably, only one switch does so at a time, limiting the loading seen by the memory controller.

Abstract: A test system includes respective clock domain crossing circuits coupling memory device signals to a memory device being tested. The clock domain crossing circuit includes a ring buffer into which the respective memory device signal is latched responsive to a first clock signal. The particular buffer into which the memory device signal is latched is determined by a write pointer, which is incremented by the first clock signal. The outputs of the buffers are applied to a multiplexer, which is controlled by a read pointer to couple a memory device signal from one of the buffers to the memory device. The read pointer is incremented by a second clock signal having a timing that is adjustable and may be different from the second clock signal used to increment the read pointer in a clock domain crossing circuit for a different memory device signal.

Abstract: A memory module includes several memory devices coupled to a memory hub. The memory hub includes several link interfaces coupled to respective processors, several memory controller coupled to respective memory devices, a cross-bar switch coupling any of the link interfaces to any of the memory controllers, a write buffer and read cache for each memory device and a read synchronization module. The read synchronization module includes a write pointer, a read pointer and a buffer. The write pointer is incremented in response to the receipt of read data. The read pointer increments in response to coupling of the read data from the memory hub. A comparator compares the read pointer an the write pointer, and the comparison is used to adjust the memory timing.

Abstract: A method of operating a memory device includes placing the memory device in a persistent auto precharge mode of operation, applying a disable command to the memory device, and disabling the persistent auto precharge mode of operation in response to the applied disable command. Memory devices operating according this method may be used in memory systems that infrequently experience page hits, such as server systems, while the ability to disable the persistent auto precharge mode allows such memory devices to be used in systems that frequently experience page hits, such as graphics or input/output applications.

Abstract: A system and method for facilitating the adjustment of timing parameters between a memory controller operating in a first clock domain and a memory device operating in a second clock domain. A write pointer and a read pointer are monitored to provide a write-read pointer offset representing the timing between when read data is made available by the memory device and when the read data is retrieved by the memory controller. Based on the write-read pointer offset, adjustment to different timing parameters can be made.

Abstract: A memory system and method according to various aspects of the present invention comprises a memory and an adaptive timing system for controlling access to the memory. The adaptive timing system captures data in a data valid window (DVW) in a data signal. In one embodiment, the adaptive timing system comprises a delay circuit for sampling the data signal at a midpoint of the DVW. The adaptive timing system may also comprise an identifying circuit for identifying whether the midpoint of the DVW corresponds to an actual midpoint of the DVW and adjusting the delay circuit accordingly.

Abstract: A synchronizer system and method that can be used with a conventional adjustable delay circuit to preserve a pseudo-synchronous phase relationship between clock signals of different clock domains when the time delay of the adjustable delay circuit from which one of the clock signals is output is changed.

Abstract: A system and method for facilitating the adjustment of timing parameters between a memory controller operating in a first clock domain and a memory device operating in a second clock domain. A write pointer and a read pointer are monitored to provide a write-read pointer offset representing the timing between when read data is made available by the memory device and when the read data is retrieved by the memory controller. Based on the write-read pointer offset, adjustment to different timing parameters can be made.

Abstract: A method and apparatus for controlling the on-die termination of a memory system. The method comprises snooping a command bus in response to a first plurality of command signals clocked at 1T and enabling the on-die termination in response to a second plurality of command signals clocked at 2T and the first plurality of command signals. The apparatus may be memory device comprising a memory array responsive to a plurality of command signals, a data bus having at least one of a data pad, a data strobe output pad, and an input data mask pad, an activation circuit responsive to certain of the plurality of command signals and operable to produce a control signal, and an termination circuit responsive to the control signal and operable to apply an effective resistance to at least one of the data pad, the data strobe output pad, and the input data mask pad.

Abstract: A synchronizer system and method that can be used with a conventional adjustable delay circuit to preserve a pseudo-synchronous phase relationship between clock signals of different clock domains when the time delay of the adjustable delay circuit from which one of the clock signals is output is changed.