Abstract: Method and system for a multi-level virtual/real cache system with synonym resolution. An exemplary embodiment includes a multi-level cache hierarchy, including a set of L1 caches associated with one or more processor cores and a set of L2 caches, wherein the set of L1 caches are a subset of the set of L2 caches, wherein the set of L1 caches underneath a given L2 cache are associated with one or more of the processor cores.

Abstract: Controlling an unreliable data transfer in a data channel from a transmitting unit to a receiving unit. A bypass mode or a buffer mode is activated depending on the error rate in the data channel. If bypass mode is selected, data packets are directly transferred in probation from the transmitting unit to the receiving unit by a bypass line. The data packets are error checked after the data transfer. If buffer mode is selected, data is transfer from the transmitting unit to the receiving unit by a buffer line via an error detecting and correcting unit and a buffer unit. The errors are detected and corrected during the data transfer.

Abstract: A method for generating a local clock domain within an operation includes steps of: receiving a clock frequency measurement for a slow portion of logic within the operation; generating a local signal to indicate commencement of the operation and to function as a clock gating signal; latching the clock gating signal to a selected cycle; generating clock domain controls based on the clock gating signal such that the operation times itscommencement on the selected cycle; and propagating the clock gating signal in ungated latches for a number of cycles, such that a second operation is restricted from being launched until the operation completes.

Abstract: A method for handling errors in a cache memory without processor core recovery includes receiving a fetch request for data from a processor and simultaneously transmitting fetched data and a parity matching the parity of the fetched data to the processor. The fetched data is received from a higher-level cache into a low level cache of the processor. Upon determining that the fetched data failed an error check indicating that the fetched data is corrupted, the method includes requesting an execution pipeline to discontinue processing and flush its contents, and initiating a clean up sequence, which includes sending an invalidation request to the low level cache causing the low level cache to remove lines associated with the corrupted data, and requesting the execution pipeline to restart. The execution pipeline accesses a copy of the requested data from a higher-level storage location.

Abstract: A method and system for verifying a logic circuit design using dynamic clock gating is disclosed. The method comprises choosing at least one master seed to determine initial values as initialization for said logic circuit and/or stimuli data for at least one interface of said logic circuit, choosing at least two different dynamic clock gating configurations for every chosen master seed, executing a functional simulation with said logic circuit for every chosen dynamic clock gating configuration by using said determined initialization and/or stimuli data based on a corresponding master seed, comparing simulation results of functional simulations against each other executed with said logic circuit for at least two different chosen dynamic clock gating configurations, and reporting an error if said at least two simulation results are not identical.

Abstract: A crossbar (20) circuit with multiplexer (22A, 22B) circuits implemented in a polygonal form on a chip. The crossbar can be used for implementing a permutation of input bits (24A, 24B) controlled by a bit vector (25). Horizontal and vertical wiring lengths in the crossbar (20) are reduced by stacking the operand latches (24A, 24B, 25) and horizontal or vertical multiplexers (22A, 22B). This implementation decreases the latency of the crossbar and avoids latches to store intermediated results, thus reducing area and power consumption.

Abstract: A method to verify an implemented coherency algorithm of a multi processor environment on a single processor model is described, comprising the steps of: generating a reference model reflecting a private cache hierarchy of a single processor within a multi processor environment, stimulating the private cache hierarchy with simulated requests and/or cross invalidations from a core side and/or from a nest side, augmenting all data available in the private cache hierarchy with two construction dates and two expiration dates, set based on interface events, wherein multi processor coherency is not observed if the cache hierarchy ever returns data to the processor with an expiration date that is older than the latest construction date of all data used before. Further a single processor model and a computer program product to execute said method are described.

Abstract: A computer implemented method of cache bounded reference counting for computer languages having automated memory management in which, for example, a reference to an object “Z” initially stored in an object “O” is fetched and the cache hardware is queried whether the reference to the object “Z” is a valid reference, is in the cache, and has a continuity flag set to “on”. If so, the object “O” is locked for an update, a reference counter is decremented for the object “Z” if the object “Z” resides in the cache, and a return code is set to zero to indicate that the object “Z” is de-referenced and that its storage memory can be released and re-used if the reference counter for the object “Z” reaches zero. Thereafter, the cache hardware is similarly queried regarding an object “N” that will become a new reference of object “O”.

Abstract: Method and system for a multi-level virtual/real cache system with synonym resolution. An exemplary embodiment includes a multi-level cache hierarchy, including a set of L1 caches associated with one or more processor cores and a set of L2 caches, wherein the set of L1 caches are a subset of the set of L2 caches, wherein the set of L1 caches underneath a given L2 cache are associated with one or more of the processor cores.

Abstract: A method for handling errors in a cache memory without processor core recovery includes receiving a fetch request for data from a processor and simultaneously transmitting fetched data and a parity matching the parity of the fetched data to the processor. The fetched data is received from a higher-level cache into a low level cache of the processor. Upon determining that the fetched data failed an error check indicating that the fetched data is corrupted, the method includes requesting an execution pipeline to discontinue processing and flush its contents, and initiating a clean up sequence, which includes sending an invalidation request to the low level cache causing the low level cache to remove lines associated with the corrupted data, and requesting the execution pipeline to restart. The execution pipeline accesses a copy of the requested data from a higher-level storage location.

Abstract: Controlling an unreliable data transfer in a data channel from a transmitting unit to a receiving unit. A bypass mode or a buffer mode is activated depending on the error rate in the data channel. If bypass mode is selected, data packets are directly transferred in probation from the transmitting unit to the receiving unit by a bypass line. The data packets are error checked after the data transfer. If buffer mode is selected, data is transfer from the transmitting unit to the receiving unit by a buffer line via an error detecting and correcting unit and a buffer unit. The errors are detected and corrected during the data transfer.

Abstract: A method and system for improving the performance of a cache. The cache may include an array of tag entries where each tag entry includes an additional bit (“reused bit”) used to indicate whether its associated cache line has been reused, i.e., has been requested or referenced by the processor. By tracking whether a cache line has been reused, data (cache line) that may not be reused may be replaced with the new incoming cache line prior to replacing data (cache line) that may be reused. By replacing data in the cache memory that might not be reused prior to replacing data that might be reused, the cache hit may be improved thereby improving performance.

Abstract: A method for generating a local clock domain within an operation includes steps of: receiving a clock frequency measurement for a slow portion of logic within the operation; generating a local signal to indicate commencement of the operation and to function as a clock gating signal; latching the clock gating signal to a selected cycle; generating clock domain controls based on the clock gating signal such that the operation times its commencement on the selected cycle; and propagating the clock gating signal in ungated latches for a number of cycles, such that a second operation is restricted from being launched until the operation completes.

Abstract: Systems and methods for adaptively mapping system memory address bits into an instruction tag and an index into the cache are disclosed. More particularly, hardware and software are disclosed for observing collisions that occur for a given mapping of system memory bits into a tag and an index. Based on the observations, an optimal mapping may be determined that minimizes collisions.

Abstract: A method and system for improving the performance of a cache. The cache may include an array of tag entries where each tag entry includes an additional bit (“reused bit”) used to indicate whether its associated cache line has been reused, i.e., has been requested or referenced by the processor. By tracking whether a cache line has been reused, data (cache line) that may not be reused may be replaced with the new incoming cache line prior to replacing data (cache line) that may be reused. By replacing data in the cache memory that might not be reused prior to replacing data that might be reused, the cache hit may be improved thereby improving performance.

Abstract: A method and system for improving the performance of a cache. The cache may include an array of tag entries where each tag entry includes an additional bit (“reused bit”) used to indicate whether its associated cache line has been reused, i.e., has been requested or referenced by the processor. By tracking whether a cache line has been reused, data (cache line) that may not be reused may be replaced with the new incoming cache line prior to replacing data (cache line) that may be reused. By replacing data in the cache memory that might not be reused prior to replacing data that might be reused, the cache hit may be improved thereby improving performance.

Abstract: A crossbar (20) circuit with multiplexer (22A, 22B) circuits implemented in a polygonal form on a chip. The crossbar can be used for implementing a permutation of input bits (24A, 24B) controlled by a bit vector (25). Horizontal and vertical wiring lengths in the crossbar (20) are reduced by stacking the operand latches (24A, 24B, 25) and horizontal or vertical multiplexers (22A, 22B). This implementation decreases the latency of the crossbar and avoids latches to store intermediated results, thus reducing area and power consumption.

Abstract: A method and system for improving the performance of a cache. The cache may include an array of tag entries where each tag entry includes an additional bit (“reused bit”) used to indicate whether its associated cache line has been reused, i.e., has been requested or referenced by the processor. By tracking whether a cache line has been reused, data (cache line) that may not be reused may be replaced with the new incoming cache line prior to replacing data (cache line) that may be reused. By replacing data in the cache memory that might not be reused prior to replacing data that might be reused, the cache hit may be improved thereby improving performance.

Abstract: Systems and methods for adaptively mapping system memory address bits into an instruction tag and an index into the cache are disclosed. More particularly, hardware and software are disclosed for observing collisions that occur for a given mapping of system memory bits into a tag and an index. Based on the observations, an optimal mapping may be determined that minimizes collisions.

Abstract: The present invention relates to data processing systems with built-in error recovery from a given checkpoint. In order to checkpoint more than one instruction per cycle it is proposed to collect updates of a predetermined maximum number of register contents performed by a respective plurality of CISC/RISC instructions in a buffer (CSB)(60) for checkpoint states, whereby a checkpoint state comprises as many buffer slots as registers can be updated by said plurality of CISC instructions and an entry for a Program Counter value associated with the youngest external instruction of said plurality, and to update an Architected Register Array (ARA)(64) with freshly collected register data after determining that no error was detected in the register data after completion of said youngest external instruction of said plurality of external instructions.