Abstract: The illustrative embodiments described herein provide a computer-implemented method, apparatus, and a system for managing instructions. A load/store unit receives a first instruction at a port. The load/store unit rejects the first instruction in response to determining that the first instruction has a first reject condition. Then, the instruction sequencing unit activates a first bit in response to the load/store unit rejection the first instruction. The instruction sequencing unit blocks the first instruction from reissue while the first bit is activated. The processor unit determines a class of rejection of the first instruction. The instruction sequencing unit starts a timer. The length of the timer is based on the class of rejection of the first instruction. The instruction sequencing unit resets the first bit in response to the timer expiring. The instruction sequencing unit allows the first instruction to become eligible for reissue in response to resetting the first bit.

Abstract: A data processing system includes a processor, a unit that includes a multi-level cache, a prefetch system and a memory. The data processing system can operate in a first mode and a second mode. The prefetch system can change behavior in response to a desired power consumption policy set by an external agent or automatically via hardware based on on-chip power/performance thresholds.

Abstract: A management system that controls a restart interface in a data processing system. The management system switches control of the interface from a distributed network managed by the caches to the management system. The management system is capable of detecting errors and seizing control of the interface in order to remedy any errors that occur within the interface.

Abstract: A method, system and computer program product for optimizing EPN to RPN translation when a data miss occurs. The method, system and computer program product take advantage of the high-likelihood of finding the matching PTE in the first half of the PTEG and utilize early data-coming signals from the L2 cache to prime the data-flow pipe to the D-ERAT arrays and requesting a joint steal cycle for executing the write into the D-ERAT and a restart request for re-dispatching the next-to-complete instruction.

Abstract: A method and system for maintaining a best-case demand redispatch of an instruction to allow for maximizing the time a rejected thread may execute in lookahead execution mode, while maintaining the smallest L1 cache miss penalty supported by the memory subsystem. In response to a demand miss, a load/store unit sends a fetch request to the next level cache. The cache line of the demand miss is examined to identify the critical sector. Once the critical sector is identified, a best-case data return time is determined based on the fastest time the next level cache is able to return the critical sector of the cache line. The load/store unit then sends a speculative warning to the dispatch unit to coincide with the best-case data return, wherein the speculative warning prepares the dispatch unit to resend the instruction for execution as soon as data is available to the processor core.

Abstract: A method and system for maintaining a best-case demand redispatch of an instruction to allow for maximizing the time a rejected thread may execute in lookahead execution mode, while maintaining the smallest L1 cache miss penalty supported by the memory subsystem. In response to a demand miss, a load/store unit sends a fetch request to the next level cache. The cache line of the demand miss is examined to identify the critical sector. Once the critical sector is identified, a best-case data return time is determined based on the fastest time the next level cache is able to return the critical sector of the cache line. The load/store unit then sends a speculative warning to the dispatch unit to coincide with the best-case data return, wherein the speculative warning prepares the dispatch unit to resend the instruction for execution as soon as data is available to the processor core.

Abstract: A method, system and computer program product for optimizing EPN to RPN translation when a data miss occurs. The method, system and computer program product take advantage of the high-likelihood of finding the matching PTE in the first half of the PTEG and utilize early data-coming signals from the L2 cache to prime the data-flow pipe to the D-ERAT arrays and requesting a joint steal cycle for executing the write into the D-ERAT and a restart request for re-dispatching the next-to-complete instruction.

Abstract: A method, apparatus, and computer program product are disclosed in a data processing system for sharing data in a cache among multiple threads in a simultaneous multi-threaded (SMT) processor. The SMT processor executes multiple threads concurrently during each clock cycle. The cache is dynamically allocated for use among the multiple threads. Portions of the cache are capable of being designated to store private data that is used exclusively by only a first one of the threads. The portions of the cache are capable of being designated to store shared data that can be used by any one of the multiple threads. The size of the portions can be changed dynamically during execution of the threads.

Abstract: A method, system, and computer program product for supporting multiple fetch requests to the same congruence class in an n-way set associative cache. Responsive to receiving an incoming fetch instruction at a load/store unit, outstanding valid fetch entries in the n-way set associative cache that have the same cache congruence class as the incoming fetch instruction are identified. SetIDs in used by these identified outstanding valid fetch entries are determined. A resulting setID is assigned to the incoming fetch instruction based on the identified setIDs, wherein the resulting setID assigned is a setID not currently in use by the outstanding valid fetch entries. The resulting setID for the incoming fetch instruction is written in a corresponding entry in the n-way set associative cache.

Abstract: A data processing system including a processor having a load/store unit and method for utilizing alias hit signals to detect errors within the read address tag arrays. Within a load store unit, implemented within a processor, a real address tag array is utilized to indicate when effective address aliasing occurs in a primary cache array. If aliasing occurs, Alias Hit signals are then used to clear any aliased entries. These Alias Hit signals can also be utilized to determine if there has been some type of failure within the real address tag array.

Abstract: A method for optimally issuing instructions that are related to a first instruction in a data processing system is disclosed. The processing system includes a primary and secondary cache. The method and system comprises speculatively indicating a hit of the first instruction in a secondary cache and releasing the dependent instructions. The method and system includes determining if the first instruction is within the secondary cache. The method and system further includes providing data related to the first instruction from the secondary cache to the primary cache when the instruction is within the secondary cache. A method and system in accordance with the present invention causes instructions that create dependencies (such as a load instruction) to signal an issue queue (which is responsible for issuing instructions with resolved conflicts) in advance, that the instruction will complete in a predetermined number of cycles.

Abstract: A method and system of facilitating storage accesses within a multiprocessor system subsequent to a synchronization instruction by a local processor consists of determining if data for the storage accesses is cacheable and if there is a “hit” in a cache. If both conditions are met, the storage accesses return the data to the local processor. The storage accesses have an entry on an interrupt table which is used to discard the returned data if a snoop kills the line before the synchronization instruction completes. After the cache returns data, a return data bit is set in the interrupt table. A snoop killing the line sets a snooped bit in the interrupt table. Upon completion of the synchronization instruction, any entries in the interrupt table subsequent to the synchronization instruction that have the return data bit and snooped bit set are flushed.

Abstract: In a load/store unit within a microprocessor, load and store instructions are executed out of order. The load and store instructions are assigned tags in a predetermined manner, and then assigned to load and store reorder queues for keeping track of the program order of the load and store instructions. When a load instruction is issued for execution, a determination is made whether the load instruction is attempting to load data to a memory location that is the same as a previously executed store instruction is waiting to complete. If so, then the data waiting to be stored within the cache by the store instruction is directly forwarded to the load instruction.

Abstract: Pipelining and parallel execution of multiple load instructions is performed within a load store unit. When a first load instruction incurs a cache miss and proceeds to retrieve the load data from the system memory hierarchy, a second load instruction addressing the same load data will be merged into the first load instruction so that the data returned from the system memory hierarchy is sent to register files associated with both the first and second load instructions. As a result, the second load instruction does not have to wait until the load data has been written and validated in the data cache.

Abstract: In a load/store unit within a microprocessor, load and store instructions are executed out of order. The load and store instructions are assigned tags in a predetermined manner, and then assigned to load and store reorder queues for keeping track of the program order of the load and store instructions. Then when new load or store instructions are issued, the new load or store instructions are compared to entries within the load and store reorder queues to detect out of order problems.

Abstract: In a load/store unit within a microprocessor, load instructions are executed out of order. The load instructions are assigned tags in a predetermined manner, and then assigned to a load reorder queue for keeping track of the program order of the load instructions. Then when new load instructions are issued, the new load instructions are compared to entries within the load reorder queues to detect out of order problems.

Abstract: A processor (100) includes an issue unit (125) having an issue queue (144) for issuing instructions to an execution unit (140). The execution unit (140) may accept and execute the instruction or produce a reject signal. After each instruction is issued, the issue queue (144) retains the issued instruction for a critical period. After the critical period, the issue queue (144) may drop the issued instruction unless the execution unit (140) has generated a reject signal. If the execution unit (140) has generated a reject signal, the instruction is eventually marked in the issue queue (144) as being available to be reissued. The length of time that the rejected instruction is held from reissue may be modified depending upon the nature of the rejection by the execution unit (140). Also, the execution unit (140) may conduct corrective actions in response to certain reject conditions so that the instruction may be fully executed upon reissue.

Abstract: A system and method for determining an age function by performing a logical function on each entry residing within a queue, determining when a particular one of the entries residing in the queue was stored in the queue relative to the other entries, and determining an oldest or youngest entry residing in the queue relative to the logical functions performed on each of the instructions. In one embodiment of the present invention, the entries are instructions temporarily stored within a queue in the processor. The logical function performed may determine which of the instructions is valid. The queue may be cyclical.