Abstract: A non-uniform memory access (NUMA) computer system includes at least two nodes coupled by a node interconnect, where at least one of the nodes includes a processor for servicing interrupts. The nodes are partitioned into external interrupt domains so that an external interrupt is always presented to a processor within the external interrupt domain in which the interrupt occurs. Although each external interrupt domain typically includes only a single node, interrupt channeling or interrupt funneling may be implemented to route external interrupts across node boundaries for presentation to a processor. Once presented to a processor, interrupt handling software may then execute on any processor to service the external interrupt. Servicing external interrupts is expedited by reducing the size of the interrupt handler polling chain as compared to prior art methods.

Abstract: A data recirculation apparatus for a data processing system includes at least one output buffer from which data are output onto an interconnect, a plurality of input storage areas from which data are selected for storage within the output buffer, and selection logic that selects data from the plurality of input storage areas for storage within the output buffer. In addition, the data recirculation apparatus includes buffer control logic that, in response to a determination that a particular datum has stalled in the output buffer, causes the particular datum to be removed from the output buffer and stored in one of the plurality of input storage areas. In one embodiment, the recirculated data has a dedicated input storage area.

Abstract: A non-uniform memory access (NUMA) computer system includes first and second processing nodes that are each coupled to a node interconnect. The first processing node includes a system memory and first and second processors that each have a respective one of first and second cache hierarchies, which are coupled for communication by a local interconnect. The second processing node includes at least a system memory and a third processor having a third cache hierarchy. The first cache hierarchy and the third cache hierarchy are permitted to concurrently store an unmodified copy of a particular cache line in a Recent coherency state from which the copy of the particular cache line can be sourced by shared intervention.

Abstract: A data processing system is disclosed which includes a first processor having an m-byte data width, an n-byte data bus, where n is less than m, and a second processor electrically coupled to the bus which performs bus transactions utilizing n-byte packets of data. An adaptor is electrically coupled between the first processor and the bus which converts n-byte packets of data input from the bus to m-byte packets of data, and converts m-byte packets of data input from the first processor to n-byte packets of data, thereby enabling the first processor to transmit data to and receive data from the bus utilizing m-byte packets of data. In a second aspect of the present invention, a method and system are provided for arbitrating between two bus masters having disparate bus acquisition protocols. In response to a second bus master asserting a bus request when a first bus master controls the bus, control of the bus is removed from the first bus master.

Abstract: A non-uniform memory access (NUMA) computer system includes a node interconnect and a plurality of processing nodes that each contain at least one processor, a local interconnect, a local system memory, and a node controller coupled to both a respective local interconnect and the node interconnect. According to the method of the present invention, a communication transaction is transmitted on the node interconnect from a local processing node to a remote processing node. In response to receipt of the communication transaction by the remote processing node, a response including a coherency response field is transmitted on the node interconnect from the remote processing node to the local processing node. In response to receipt of the response at the local processing node, a request is issued on the local interconnect of the local processing node concurrently with a determination of a coherency response indicated by the coherency response field.

Abstract: A non-uniform memory access (NUMA) data processing system includes a node interconnect to which at least a first processing node and a second processing node are coupled. The first and the second processing nodes each include a local interconnect, a processor coupled to the local interconnect, a system memory coupled to the local interconnect, and a node controller interposed between the local interconnect and the node interconnect. In order to reduce communication latency, the node controller of the first processing node speculatively transmits request transactions received from the local interconnect of the first processing node to the second processing node via the node interconnect. In one embodiment, the node controller of the first processing node subsequently transmits a status signal to the node controller of the second processing node in order to indicate how the request transaction should be processed at the second processing node.

Abstract: A computer system includes a node interconnect to which at least a first processing node and a second processing node are coupled. The first and the second processing nodes each include a local interconnect, a processor coupled to the local interconnect, a system memory coupled to the local interconnect, and a node controller interposed between the local interconnect and the node interconnect. In order to reduce communication latency, the node controller of the first processing node speculatively transmits request transactions received from the local interconnect of the first processing node to the second processing node via the node interconnect, where each such request transaction specifies an associated datum. The node controller of the second processing node handles each speculatively transmitted request transaction received in response to a directory state of its associated datum.

Abstract: A non-uniform memory access (NUMA) computer system includes an interconnect to which multiple processing nodes (including first, second, and third processing nodes) are coupled. Each of the first, second, and third processing nodes includes at least one processor and a local system memory. The NUMA computer system further includes a transaction buffer, coupled to the interconnect, that stores communication transactions transmitted on the interconnect that are both initiated by and targeted at a processing node other than the third processing node. In response to a determination that a particular communication transaction originally targeting another processing node should be processed by the third processing node, buffer control logic coupled to the transaction buffer causes the particular communication transaction to be retrieved from the transaction buffer and processed by the third processing node.

Abstract: A data processing system is disclosed which includes a first processor having an m-byte data width, an n-byte data bus, where n is less than m, and a second processor electrically coupled to the bus which performs bus transactions utilizing n-byte packets of data. An adaptor is electrically coupled between the first processor and the bus which converts n-byte packets of data input from the bus to m-byte packets of data, and converts m-byte packets of data input from the first processor to n-byte packets of data, thereby enabling the first processor to transmit data to and receive data from the bus utilizing m-byte packets of data. In a second aspect of the present invention, a method and system are provided for arbitrating between two bus masters having disparate bus acquisition protocols. In response to a second bus master asserting a bus request when a first bus master controls the bus, control of the bus is removed from the first bus master.

Abstract: A power supply interface suitable to provide voltages of appropriate magnitude to a static random access memory (SRAM) device from a combination of independent sources including a main power supply, an auxiliary power supply, and a battery. The voltages from the interface are at levels consistent with the SRAM modes of operation. During limited voltage tolerance read and write access operations, main power supply voltage is provided through a low forward voltage drop switched metal oxide field effect transistor (MOSFET). Parasitic paths, potentially producible by the transistor and affecting the battery source of power, are eliminated through the use of a second, complementary MOSFET. The second MOSFET is directly responsive to a POWERGOOD signal from the main power supply, indicating both an "on" state and an appropriate voltage level of the main power supply.

Abstract: A method and apparatus in a data processing system having a plurality of node controllers and a memory unit for each of the node controllers. Each one of the node controllers including at least one processor having a cache. Each memory unit including a plurality of entries each having an exclusive bit, an address tag, and an inclusion field. Each bit of the inclusion field representing one of the node controllers. The method and apparatus allow error recovery for errors occurring within the entries without using the ECC implementation. Specifically, two parity bits are used for detecting errors within an entry and logic for flushing any cache lines represented by the entry in error. The method and apparatus also includes means for detecting persistent errors and for indicating whether the error is generated by either hardware or software.

Abstract: Systems and methods for reducing the thermal stresses between an integrated circuit package and a printed circuit board, each having different thermal coefficients of expansion, to minimize thermal fatigue induced by power management cycling. The thermal impedance of the convection cooling system used with the integrated circuit package is switched with the state of the power management signal. A fan on the integrated circuit package heat sink is energized when the integrated circuit is operated in a high power mode and disabled when the integrated circuit is in a low power mode initiated by the power management system. The switching is directly responsive to the power management system and without regard to integrated circuit package temperature. The switching of the fan alters the thermal impedance to reduce the extremes of the temperature excursion and to materially reduce the rate of change of temperature experienced by the integrated circuit package.