Abstract: A memory system comprising memory modules including memory chips stacked with switching circuits. A memory controller coupled to the memory modules is configured to initiate memory accesses. When a stacked switching circuit detects the memory access, the switching circuit routes the access to another memory module if the access is not directed to a memory chip of the receiving memory module, or processes the access locally if the access is directed to a memory chip of the receiving memory module. The memory controller and memory modules are coupled via bi-directional serial links. Each memory module may include multiple stacked switching circuits, each of which may be coupled to fewer than all of the memory chips within the memory module. Switching circuits further include circuitry configured to de-serialize data prior to conveyance to a memory chip, and serialize data received from a DRAM chip prior to transmitting the received data.

Abstract: In one embodiment, a memory controller is coupled to a memory subsystem and controls accesses to the memory subsystem. In addition, a temperature sensor is positioned to detect a temperature associated with the memory subsystem. In this embodiment, the memory controller is configured to selectively insert one or more idle clock cycles between a first memory access and a second memory access depending upon the sensed temperature. In a further embodiment, a sensor is positioned to detect a power condition associated with the memory subsystem. In this embodiment, the memory controller is configured to selectively insert one or more idle clock cycles between a first memory access and a second memory access depending upon the detected power condition.

Abstract: A redundant clock distribution system with spread spectrum. In one embodiment, a clock board includes a clock synthesizer configured to provide an input clock signal, and a spread spectrum unit coupled to receive the input clock signal. The spread spectrum unit is configured to frequency modulate the input clock signal, thereby producing an output clock signal wherein energy of the output clock signal is spread over a range of frequencies.

Abstract: A method and apparatus for controlling a DRAM refresh rate. In one embodiment, a computer system includes a memory subsystem having a memory controller and one or more DRAM (dynamic random access memory) devices. The memory controller is configured to periodically initiate a refresh cycle to the one or more DRAM devices. The memory controller is also configured to monitor the temperature of the one or more DRAM devices. If the temperature exceeds a preset threshold, the memory controller is configured to increase the rate at which the periodic refresh cycle is performed.

Abstract: In one embodiment, a memory controller is coupled to a memory subsystem and controls accesses to the memory subsystem. In addition, a temperature sensor is positioned to detect a temperature associated with the memory subsystem. In this embodiment, the memory controller is configured to selectively insert one or more idle clock cycles between a first memory access and a second memory access depending upon the sensed temperature. In a further embodiment, a sensor is positioned to detect a power condition associated with the memory subsystem. In this embodiment, the memory controller is configured to selectively insert one or more idle clock cycles between a first memory access and a second memory access depending upon the detected power condition.

Abstract: A clock distribution architecture having clock and power failure protection is disclosed. In one embodiment, a computer system includes a plurality of client boards and a plurality of switch boards, as well as having power distribution boards and clock boards (referred to herein as service processor boards). In one embodiment may include a clock board and a plurality of power distribution boards, while another embodiment may include a power distribution board and a plurality of clock boards. The clock board(s) may generate a global clock signal, which may be distributed to the switch boards and the power distribution board(s). The power distribution board(s) may distribute the global clock signal to the client boards. Clock redundancy may be provide through either having multiple clock boards or multiple power distribution boards.

Abstract: A clock architecture employing redundant clock synthesizers is disclosed. In one embodiment, a computer system includes first and second clock boards. The first clock board may act as a master, generating a system clock signal, while the second clock board acts as a slave. The first clock board may monitor a phase difference between a first crystal clock signal and a feedback clock signal. If the phase difference exceeds a limit, the first crystal clock signal may be inhibited, preventing the first clock board from generating the system clock signal. The second clock board may monitor the system clock board in reference to a feedback clock signal. If the second clock board detects a predetermined number of consecutive missing clock edges, it may enable a second crystal clock signal, which may be used to generate a system clock signal.

Abstract: A memory subsystem including memory modules having multiple banks. A memory subsystem includes a memory controller and a plurality of memory modules. The plurality of memory modules may be coupled to the memory controller by a memory interconnect having a data path including a plurality of data bits. Each of the plurality of memory modules includes a circuit board and a plurality of memory chips mounted to the circuit board. The circuit board includes a connector edge for connection to the memory interconnect. Each of the plurality of memory chips may be configured to store data in a plurality of storage locations. Each of the plurality of memory modules may be coupled to a respective mutually exclusive subset of the plurality of data bits.

Abstract: A circuit topology for high-speed memory access. In one embodiment, an electronic circuit includes a memory controller. The memory controller is coupled to a memory module by a first plurality of transmission lines. The memory module may include a second plurality of transmission lines coupled to the first plurality. The memory module further includes a first memory bank coupled to the second plurality of transmission lines and a third plurality of transmission lines. A second memory bank may be coupled to the third plurality of transmission lines. Each of the first, second, and third pluralities of transmission lines may be part of a common bus.

Abstract: A data strobe receiver that includes a first comparator. The first comparator has a first input that is coupled to a first reference voltage. The first comparator has a second input that is coupled to a data strobe. The first comparator also has an output. The data strobe receiver also includes a delay element. The delay element has an input that is coupled to the output of the first comparator. The delay element also has an enable input and an output. The data strobe receiver also includes a second comparator. The second comparator has a first input that is coupled to a second voltage reference. The second comparator has a second input that is coupled to the data strobe. The second comparator also has an output. The data strobe receiver also includes a divide-by-X-counter, where X is an integer greater than 1 and less than 129. The divide-by-X-counter has an input that is coupled to the output of the second comparator.

Abstract: A memory integrated circuit including an error detection mechanism for detecting errors in address and control signals. The memory integrated circuit includes a memory array including a plurality of memory cells configured to store data. The memory integrated circuit also includes an address logic unit coupled to the memory array which may be configured to receive a plurality of memory requests each including address information and corresponding error detection information. The corresponding error detection information may be dependent upon the address information. The memory integrated circuit further includes error detection logic which is coupled to the address logic and may be configured to detect an error in the address information based upon the corresponding error detection information and may provide an error indication in response to detecting the error.

Abstract: A memory subsystem including memory modules having multiple banks. A memory subsystem includes a memory controller and a plurality of memory modules. The plurality of memory modules may be coupled to the memory controller by a memory interconnect having a data path including a plurality of data bits. Each of the plurality of memory modules includes a circuit board and a plurality of memory chips mounted to the circuit board. The circuit board includes a connector edge for connection to the memory interconnect. Each of the plurality of memory chips may be configured to store data in a plurality of storage locations. Each of the plurality of memory modules may be coupled to a respective mutually exclusive subset of the plurality of data bits.

Abstract: A circuit topology for high-speed memory access. In one embodiment, an electronic circuit includes a memory controller. The memory controller is coupled to a memory module by a first plurality of transmission lines. The memory module may include a second plurality of transmission lines coupled to the first plurality. The memory module further includes a first memory bank coupled to the second plurality of transmission lines and a third plurality of transmission lines. A second memory bank may be coupled to the third plurality of transmission lines. Each of the first, second, and third pluralities of transmission lines may be part of a common bus.

Abstract: A clock architecture employing redundant clock synthesizers is disclosed. In one embodiment, a computer system includes first and second clock boards. The first clock board may act as a master, generating a system clock signal, while the second clock board acts as a slave. The first clock board may monitor a phase difference between a first crystal clock signal and a feedback clock signal. If the phase difference exceeds a limit, the first crystal clock signal may be inhibited, preventing the first clock board from generating the system clock signal. The second clock board may monitor the system clock board in reference to a feedback clock signal. If the second clock board detects a predetermined number of consecutive missing clock edges, it may enable a second crystal clock signal, which may be used to generate a system clock signal.

Abstract: A method and apparatus for providing a differential clock signal to a plurality of memory modules. In one embodiment, an electronic circuit (e.g. computer system motherboard) includes a clock generating circuit and one or more memory modules. The memory modules may be coupled to receive a differential clock signal from the clock generating circuit via a pair of transmission lines. Each transmission line may be coupled to one of the differential clock inputs on the memory module by a series-connected resistor. Since the differential clock inputs for each memory module are coupled to the transmission lines by series-connected resistors, the changing of the memory module population may have a minimal effect on capacitive loading, and thus delays, than on memory modules where the differential clock inputs are terminated by parallel-connected resistors.

Abstract: A clock distribution architecture having clock and power failure protection is disclosed. In one embodiment, a computer system includes a plurality of client boards and a plurality of switch boards, as well as having power distribution boards and clock boards (referred to herein as service processor boards). In one embodiment may include a clock board and a plurality of power distribution boards, while another embodiment may include a power distribution board and a plurality of clock boards. The clock board(s) may generate a global clock signal, which may be distributed to the switch boards and the power distribution board(s). The power distribution board(s) may distribute the global clock signal to the client boards. Clock redundancy may be provide through either having multiple clock boards or multiple power distribution boards.

Abstract: A bi-directional output buffer includes active termination and separate driving and receiving impedances. The buffer has at least a driving mode and a receiving mode. In driving mode, the output impedance of the buffer is calibrated to a specified strength. In receiving mode, the buffer is calibrated to another specified impedance as an active termination. In addition, the buffer may be configured such that resistive components are shared in driving and receiving modes.

Abstract: A bidirectional output buffer includes active termination and separate driving and receiving impedances. The buffer has at least a driving mode and a receiving mode. In driving mode, the output impedance of the buffer is calibrated to a specified strength. In receiving mode, the buffer is calibrated to another specified impedance as an active termination. In addition, the buffer may be configured such that resistive components are shared in driving and receiving modes.

Abstract: An on-chip DC voltage generator providing a marginable reference voltage signal is described. The present invention is a CMOS-based integrated circuit that generates a marginable reference voltage level. The present invention provides a process insensitive reference voltage signal and may be configured so as to generate a ground-bounce-noise free signal.

Abstract: An on-chip DC voltage generator providing a marginable reference voltage signal is described. The present invention is a CMOS-based integrated circuit that generates a marginable reference voltage level. The present invention provides a process insensitive reference voltage signal and may be configured so as to generate a ground-bounce-noise free signal.