| Patent application number | Description | Published |
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| 20080263325 | SYSTEM AND STRUCTURE FOR SYNCHRONIZED THREAD PRIORITY SELECTION IN A DEEPLY PIPELINED MULTITHREADED MICROPROCESSOR - A microprocessor and system with improved performance and power in simultaneous multithreading (SMT) microprocessor architecture. The microprocessor and system includes a process wherein the processor has the ability to select instructions from one thread or another in any given processor clock cycle. Instructions from each, thread may be assigned selection priorities at multiple decision points in a processor in a given cycle dynamically. The thread priority is based on monitoring performance behavior and activities in the processor. In the exemplary embodiment, the present invention discloses a microprocessor and system for synchronizing thread priorities among multiple decision points throughout the micro-architecture of the microprocessor. This system and method for synchronizing thread priorities allows each thread priority to he in sync and aware of the status of other thread priorities at various decision points within the microprocessor. | 10-23-2008 |
| 20080307210 | System and Method for Optimizing Branch Logic for Handling Hard to Predict Indirect Branches - A system and method for optimizing the branch logic of a processor to improve handling of hard to predict indirect branches are provided. The system and method leverage the observation that there will generally be only one move to the count register (mtctr) instruction that will be executed while a branch on count register (bcctr) instruction has been fetched and not executed. With the mechanisms of the illustrative embodiments, fetch logic detects that it has encountered a bcctr instruction that is hard to predict and, in response to this detection, blocks the target fetch from entering the instruction buffer of the processor. At this point, the fetch logic has fetched all the instructions up to and including the bcctr instruction but no target instructions. When the next mtctr instruction is executed, the branch logic of the processor grabs the data and starts fetching using that target address. Since there are no other target instructions that were fetched, no flush is needed if that target address is the correct address, i.e. the branch prediction is correct. | 12-11-2008 |
| 20090049286 | DATA PROCESSING SYSTEM, PROCESSOR AND METHOD OF DATA PROCESSING HAVING IMPROVED BRANCH TARGET ADDRESS CACHE - A processor includes an execution unit and instruction sequencing logic that fetches instructions from a memory system for execution. The instruction sequencing logic includes branch logic that outputs predicted branch target addresses for use as instruction fetch addresses. The branch logic includes a level one branch target address cache (BTAC) and a level two BTAC each having a respective plurality of entries each associating at least a tag with a predicted branch target address. The branch logic accesses the level one and level two BTACs in parallel with a tag portion of a first instruction fetch address to obtain a first predicted branch target address from the level one BTAC for use as a second instruction fetch address in a first processor clock cycle and a second predicted branch target address from the level two BTAC for use as a third instruction fetch address in a later second processor clock cycle. | 02-19-2009 |
| 20090198962 | DATA PROCESSING SYSTEM, PROCESSOR AND METHOD OF DATA PROCESSING HAVING BRANCH TARGET ADDRESS CACHE INCLUDING ADDRESS TYPE TAG BIT - In at least one embodiment, a processor includes an execution unit and instruction sequencing logic that fetches instructions from a memory system for execution by the execution unit. The instruction sequencing logic includes branch logic that outputs predicted branch target addresses for use as instruction fetch addresses. The branch logic includes a branch target address prediction circuitry concurrently holding a first entry providing storage for a first branch target address prediction associating a first instruction fetch address with a first branch target address to be used as an instruction fetch address and a second entry providing storage for a second branch target address prediction associating the first instruction fetch address with a different second branch target address. The first entry indicates a first instruction address type for the first instruction fetch address, and the second entry indicates a second instruction address type for the first instruction fetch address. | 08-06-2009 |
| 20090198981 | DATA PROCESSING SYSTEM, PROCESSOR AND METHOD OF DATA PROCESSING HAVING BRANCH TARGET ADDRESS CACHE STORING DIRECT PREDICTIONS - In at least one embodiment, a processor includes at least one execution unit and instruction sequencing logic that fetches instructions for execution by the execution unit. The instruction sequencing logic includes branch logic that outputs predicted branch target addresses for use as instruction fetch addresses. The branch logic includes a branch target address cache (BTAC) having at least one direct entry providing storage for a direct branch target address prediction associating a first instruction fetch address with a branch target address to be used as a second instruction fetch address immediately after the first instruction fetch address and at least one indirect entry providing storage for an indirect branch target address prediction associating a third instruction fetch address with a branch target address to be used as a fourth instruction fetch address subsequent to both the third instruction fetch address and an intervening fifth instruction fetch address. | 08-06-2009 |
| 20090198982 | DATA PROCESSING SYSTEM, PROCESSOR AND METHOD OF DATA PROCESSING HAVING BRANCH TARGET ADDRESS CACHE SELECTIVELY APPLYING A DELAYED HIT - In at least one embodiment, a processor includes at least one execution unit that executes instructions and instruction sequencing logic, coupled to the at least one execution unit, that fetches instructions from a memory system for execution by the at least one execution unit. The instruction sequencing logic including branch target address prediction circuitry that stores a branch target address prediction associating a first instruction fetch address with a branch target address to be used as a second instruction fetch address. The branch target address prediction circuitry includes delay logic that, in response to at least a tag portion of a third instruction fetch address matching the first instruction fetch address, delays access to the memory system utilizing the second instruction fetch address if no branch target address prediction was made in an immediately previous cycle of operation. | 08-06-2009 |
| 20090198983 | GLOBAL HISTORY FOLDING TECHNIQUE OPTIMIZED FOR TIMING - A global history vector (GHV) mechanism maintains a folded GHV with higher order entries an an unfolded GHV with lower order entries. When a new entry arrives at the GHV, the GHV mechanism performs an XOR of the oldest unfolded entry in the unfolded GHV with the new entry. The XOR result is then shifted into the folded GHV as the newest folded entry. The oldest folded entry is discarded during the shift in of the newest folded entry. The GHV mechanism thus provides a resulting folded GHV that is current and can be utilized for XORing with an IFAR by performing an XOR operation. Only a single XOR logic is required to perform a single bit XOR operation between the oldest entry and the youngest entry, resulting in reducing the cycle time required to complete the folding operation on a GHV. | 08-06-2009 |
| 20090198985 | DATA PROCESSING SYSTEM, PROCESSOR AND METHOD OF DATA PROCESSING HAVING BRANCH TARGET ADDRESS CACHE WITH HASHED INDICES - In at least one embodiment, a processor includes at least one execution unit that executes instructions and instruction sequencing logic, coupled to the at least one execution unit, that fetches instructions from a memory system for execution by the at least one execution unit. The instruction sequencing logic including a branch target address cache (BTAC) including a plurality of entries for storing branch target address predictions. The BTAC includes index logic that selects an entry to access utilizing a BTAC index based upon at least a set of higher order bits of an instruction address and a set of lower order bits of the instruction address. | 08-06-2009 |
| 20100031011 | METHOD AND APPARATUS FOR OPTIMIZED METHOD OF BHT BANKING AND MULTIPLE UPDATES - The invention relates to a method and apparatus for controlling the instruction flow in a computer system and more particularly to the predicting of outcome of branch instructions using branch prediction arrays, such as BHTs. In an embodiment, the invention allows concurrent BHT read and write accesses without the need for a multi-ported BHT design, while still providing comparable performance to that of a multi-ported BHT design. | 02-04-2010 |
| 20100262806 | Tracking Effective Addresses in an Out-of-Order Processor - Mechanisms, in a data processing system, are provided for tracking effective addresses through a processor pipeline of the data processing system. The mechanisms comprise logic for fetching an instruction from an instruction cache and associating, by an effective address table logic in the data processing system, an entry in an effective address table (EAT) data structure with the fetched instruction. The mechanisms further comprise logic for associating an effective address tag (eatag) with the fetched instruction, the eatag comprising a base eatag that points to the entry in the EAT and an eatag offset. Moreover, the mechanisms comprise logic for processing the instruction through the processor pipeline by processing the eatag. | 10-14-2010 |
| 20110131438 | Saving Power by Powering Down an Instruction Fetch Array Based on Capacity History of Instruction Buffer - Mechanisms for saving power by powering down an instruction fetch array based on capacity history information of an instruction buffer are provided. The mechanisms operate to receive a current access to an instruction buffer of a processor. The current access is a fetch of a group of one or more instructions to be stored in the instruction buffer. A determination is made, for one or more prior accesses occurring prior to the current access, if a predetermined pattern of capacity availability of the instruction buffer indicates that the instruction buffer is likely to have available capacity to store the group of one or more instructions of the current access. An instruction fetch unit array is powered down in response to a determination that the instruction buffer is not likely to have available capacity to store the group of one or more instructions of the current access. | 06-02-2011 |
