Abstract: Disclosed is an apparatus and means for searching a cache directory with full ECC support without the latency of the ECC logic on every directory search. The apparatus allows for bypassing the ECC logic in an attempt to search the directory. When a correctable error occurs which causes the search results to differ, a retry will occur with the corrected results used on the subsequent pass. This allows for the RAS characteristics of full ECC but the delay of the ECC path will only be experienced when a correctable error occurs, thus reducing average latency of the directory pipeline significantly. Disclosed is also a means for notifying the requester of a retry event and the ability to retry the search in the event that the directory is allowed to change between passes.

Abstract: A method of calibrating an interface is provided to automatically achieve a minimal cycle latency while maintaining synchronous data arrival between a multiplicity of self-aligning interfaces. Independent self-alignment interfaces may de-skew data bits and have them arrive on a minimum cycle boundary. However, if all the interfaces do not arrive on the same cycle, SMP designs may not function properly. For instance, with a single control chip and multiple data chips on an AMP node, the control chip often sends out controls to the dataflow chips. If the data arriving on the elastic interfaces is not synchronized with the controls, the data is not routed properly. The method employs a calibration pattern to determine the latest cycle that data is received across the elastic interfaces and calculates the target cycle for all the interfaces to match this latest cycle. The target cycle is fed back into the design and the data is received synchronously.

Abstract: A method of calibrating an elastic interface is provided to automatically achieve a minimal cycle delay through the interface. An existing self-alignment interface (i.e. elastic interface) is used to de-skew within a cycle and stage the data to have it arrive on a given, programmed target cycle. However, this target cycle must be calculated in advance and may be larger than it needs to be, causing more latency on the interface. This method is used to determine the earliest target cycle (with or without additional guard-band). This target cycle is used to adjust the interface automatically to achieve this earliest target cycle. The determination of earliest target cycle can be done once, continuously, or using a sample window. The method also can be used for interfaces that have frequency multipliers or phase shifts at its boundaries.

Abstract: An SMP computer system has an apparatus and method for recalibrating a self-timed, source-synchronous, pipelined interface while the computer system is running. The apparatus allows for quiescing the interface (ie. idling the processors to allow for no data transfers), raising fences (blocking interfaces), allowing for a quick clock centering recalibration step, and then unfencing and unquiescing to allow for the use of the interface again. The recalibration allows for compensating for drift over time on the interface to compensate for temperature, voltage, cycle time, and end-of-life degradation without bringing down and restarting the system.

Abstract: Uncorrectable errors are isolated to one component of a computing system comprising a plurality of components. First, upon detection of an uncorrectable error, a special check bit pattern is generated. This check bit pattern is used to indicate the occurrence of an uncorrectable error, as well as the location of the occurrence of the error. Subsequently, the check bit pattern is incorporated into the data word being transmitted, and thus may be used to isolate an uncorrectable error to the exact location of occurrence.

Abstract: An error correction code for single symbol error correction and double symbol error detection is generated according to a novel modular H-matrix. The H-matrix utilizes a modular design with multiple iterations of a plurality of subsets. In particular, one example of this H-matrix includes a plurality of rows and columns with each of at least one row of the H-matrix comprising, in part, multiple iterations of one subset of the plurality of subsets. The remainder of the rows, comprises, in part, a cyclic permutation of all of the remaining subsets of the plurality of subsets.

Abstract: Data is protected during conversion from one or more source error correction codes to one or more destination error correction codes by generating check bits of the destination error correction codes prior to a detection for errors in the source error correction codes. After commencing generation of these check bits, a detection is made for any errors in the source error correction codes. These errors are subsequently corrected in the destination error correction codes by complementing the erroneous bits of the destination error correction code. In addition, various logic reduction techniques may also be implemented to increase efficiency.

Abstract: Uncorrectable errors are detected during the transmission of a data word according to an error correction code. Then, any address faults are identified from among the detected uncorrectable errors. In addition, address faults as well as uncorrectable memory data failures are detected from among the detected uncorrectable errors. Furthermore, address parity bits are not required to be stored to memory.

Abstract: A system resource enable apparatus for enabling operations on a system resource including a register representing current and future operations on the resource, a pattern generator that applies a pattern corresponding to a requested resource operation to each of a plurality of requests for resource operations in a queue, compare logic that determines for each of the plurality of requests if the request will conflict with other resource operations by comparing the pattern applied to the request with the register, priority grant logic that grants priority to a request in the queue if no conflict is determined and to update the register according to the pattern applied to the request, and resource enable logic that enables operations on the resource according to the register. An automatic wake-up mechanism may also be provided to keep the array active during extended periods of non-use.

Abstract: A system resource enable apparatus for enabling operations on a system resource including a register representing current and future operations on the resource, a pattern generator that applies a pattern corresponding to a requested resource operation to each of a plurality of requests for resource operations in a queue, compare logic that determines for each of the plurality of requests if the request will conflict with other resource operations by comparing the pattern applied to the request with the register, priority grant logic that grants priority to a request in the queue if no conflict is determined and to update the register according to the pattern applied to the request, and resource enable logic that enables operations on the resource according to the register. An automatic wake-up mechanism may also be provided to keep the array active during extended periods of non-use.

Abstract: A system resource enable apparatus for enabling operations on a system resource including a register representing current and future operations on the resource, a pattern generator that applies a pattern corresponding to a requested resource operation to each of a plurality of requests for resource operations in a queue, compare logic that determines for each of the plurality of requests if the request will conflict with other resource operations by comparing the pattern applied to the request with the register, priority grant logic that grants priority to a request in the queue if no conflict is determined and to update the register according to the pattern applied to the request, and resource enable logic that enables operations on the resource according to the register.

Abstract: A system resource enable apparatus for enabling operations on a system resource including a register representing current and future operations on the resource, a pattern generator that applies a pattern corresponding to a requested resource operation to each of a plurality of requests for resource operations in a queue, compare logic that determines for each of the plurality of requests if the request will conflict with other resource operations by comparing the pattern applied to the request with the register, priority grant logic that grants priority to a request in the queue if no conflict is determined and to update the register according to the pattern applied to the request, and resource enable logic that enables operations on the resource according to the register.

Abstract: A system resource enable apparatus for enabling operations on a system resource including a register representing current and future operations on the resource, a pattern generator that applies a pattern corresponding to a requested resource operation to each of a plurality of requests for resource operations in a queue, compare logic that determines for each of the plurality of requests if the request will conflict with other resource operations by comparing the pattern applied to the request with the register, priority grant logic that grants priority to a request in the queue if no conflict is determined and to update the register according to the pattern applied to the request, and resource enable logic that enables operations on the resource according to the register.

Abstract: A system resource enable apparatus for enabling operations on a system resource including a register representing current and future operations on the resource, a pattern generator that applies a pattern corresponding to a requested resource operation to each of a plurality of requests for resource operations in a queue, compare logic that determines for each of the plurality of requests if the request will conflict with other resource operations by comparing the pattern applied to the request with the register, priority grant logic that grants priority to a request in the queue if no conflict is determined and to update the register according to the pattern applied to the request, and resource enable logic that enables operations on the resource according to the register.

Abstract: Error detection and correction circuitry, optimized to reduce the time required to correct single errors and to detect the presence of uncorrectable errors, uses an optimized H-Matrix and provides reduced logic circuitry. Correctable error syndromes are defined as comprising an odd number of ones and an uncorrectable-error detection circuit generates an uncorrectable-error indication when an even number of ones are detected. The correctable-error syndromes are defined as having a predefined combination of ones and zeros in each of a set of corresponding bit positions and different combinations of ones and zeros in other bit positions. An error syndrome comprising only zeros is designated as indicative of a no error condition. Logic circuitry is provided which implements the error detection and correction circuitry with a reduced set of logic gates.

Abstract: A resource arbitration system is provided implementing a modified round robin priority selection logic including resource checking and lockout avoidance that updates the round robin priority token only when (1) the process request is granted and (2) there are no prior processes with resource conflicts. The resource arbitration system thereby allows each process request to get into the queue with high priority once the requested resource is freed.

Abstract: A clock tuning system and method for a data processing system with enhanced timing failure diagnostics and unlayering capabilities. Both common and individual phase adjusting capabilities ensure programmable tuning of clock pulses distributed throughout a computer system, thereby facilitating isolation of timing margin failure to specific clock signals or enhancing system performance by shifting timing margin between logic paths. Both single-clock and dual-clock data processing are discussed, as well as clock tuning embodiments for each.