Abstract: A memory system is disclosed. The memory system includes first and second memory devices, and a memory controller configured to selectively enable one of the memory devices, the memory controller having a first line coupled to the first and second memory devices and a second line coupled to the first and second memory devices. The first memory device is configured to provide a notification to the memory controller on the first line and the second memory device is configured to provide a notification to the memory controller on the second line. The first memory device is further configured not to load the first line and the second memory device is further configured not to load the second line when the memory controller is writing to the enabled memory device.

Abstract: The disclosure is directed to a weakly-ordered processing system and method of executing memory barriers in weakly-ordered processing system. The processing system includes memory and a master device configured to issue memory access requests, including memory barriers, to the memory. The processing system also includes a slave device configured to provide the master device access to the memory, the slave device being further configured to produce a signal indicating that an ordering constraint imposed by a memory barrier issued by the master device will be enforced, the signal being produced before the execution of all memory access requests issued by the master device to the memory before the memory barrier.

Abstract: The disclosure is directed to a weakly-ordered processing system and method of executing memory barriers in weakly-ordered processing system. The processing system includes memory and a master device configured to issue memory access requests, including memory barriers, to the memory. The processing system also includes a slave device configured to provide the master device access to the memory, the slave device being further configured to produce a signal indicating that an ordering constraint imposed by a memory barrier issued by the master device will be enforced, the signal being produced before the execution of all memory access requests issued by the master device to the memory before the memory barrier.

Abstract: A weakly-ordered processing system implements an execution synchronization bus transaction, or “memory barrier” bus transaction, to enforce strongly-ordered data transfer bus transactions. A slave device that ensures global observability may “opt out” of the memory barrier protocol. In various embodiments, the opt-out decision may be made dynamically by each slave device asserting a signal, may be set system-wide during a Power-On Self Test (POST) by polling the slave devices and setting corresponding bits in a global observability register, or it may be hardwired by system designers so that only slave devices capable of performing out-of-order data transfer operations participate in the memory barrier protocol.

Abstract: The disclosure is directed to a weakly-ordered processing system and method of executing memory barriers in weakly-ordered processing system. The processing system includes memory and a master device configured to issue memory access requests, including memory barriers, to the memory. The processing system also includes a slave device configured to provide the master device access to the memory, the slave device being further configured to produce a signal indicating that an ordering constraint imposed by a memory barrier issued by the master device will be enforced, the signal being produced before the execution of all memory access requests issued by the master device to the memory before the memory barrier.

Abstract: In one embodiment taught herein, a memory module selectively uses its write data mask input as a status output on which it provides status signaling to an associated memory controller. The memory module configures its data mask input as a status output at one or more times not conflicting with write operations. Correspondingly, the memory controller configures its write data mask output as a status input at such times, for receipt of status signaling from the memory module. In one embodiment, the memory module maintains a status register related to one or more operating conditions of the module, such as temperature, and signals status information changes to the memory controller by driving the module's data mask input. In response to such signaling, the memory controller initiates a read of the module's status register to obtain updated status information, and takes appropriate action, such as by changing the module's refresh rate.

Abstract: Status information comprising data not stored in a memory array is efficiently read from a plurality of parallel memory devices sharing an N-bit data bus by configuring each memory device to drive the status information on a different subset M of the N bits, and tri-state the remaining N-M bits. Each memory device is additionally configured to drive zero, one or more data strobes associated with the subset M, and tri-state the remaining data strobes. A memory controller may simultaneously read status information from two or more memory devices in parallel, with each memory device driving a separate subset M of the N-bit bus. Each memory device may serialize the status information, and drive it on the subset M of the bus in burst form. Each memory device may include a configuration register initialized by a memory controller to define its subset M.