Abstract: A processor includes a decoder that decodes an instruction that instructs the processor to perform subsequent computations in an approximate manner and a functional unit that performs the subsequent computations in the approximate manner in response to the instruction. An instruction instructs the processor to clear an error amount associated with a value stored in a general purpose register of the processor. The error amount indicates an amount of error associated with a result of a computation performed by the processor in an approximate manner. The processor also clears the error amount in response to the instruction. Another instruction specifies a computation to be performed and includes a prefix that indicates the processor is to perform the computation in an approximate manner. The functional unit performs the computation specified by the instruction in the approximate manner specified by the prefix.

Abstract: A microprocessor includes a predicting unit having storage for holding a prediction history of characteristics of instructions previously executed by the microprocessor. The predicting unit accumulates the prediction history and uses the prediction history to make predictions related to subsequent instruction executions. The storage comprises a plurality of portions separately controllable for accumulating the prediction history. The microprocessor also includes a control unit that detects the microprocessor is running an operating system routine and controls the predicting unit to use only a fraction of the plurality of portions of the storage to accumulate the prediction history while the microprocessor is running the operating system routine.

Abstract: A microprocessor capable of running both x86 instruction set architecture (ISA) machine language programs and Advanced RISC Machines (ARM) ISA machine language programs. The microprocessor includes a mode indicator that indicates whether the microprocessor is currently fetching instructions of an x86 ISA or ARM ISA machine language program. The microprocessor also includes a plurality of model-specific registers (MSRs) that control aspects of the operation of the microprocessor. When the mode indicator indicates the microprocessor is currently fetching x86 ISA machine language program instructions, each of the plurality of MSRs is accessible via an x86 ISA RDMSR/WRMSR instruction that specifies an address of the MSR. When the mode indicator indicates the microprocessor is currently fetching ARM ISA machine language program instructions, each of the plurality of MSRs is accessible via an ARM ISA MRRC/MCRR instruction that specifies the address of the MSR.

Abstract: A microprocessor having performs an architectural instruction that instructs it to perform an operation on first and second source operands to generate a result and to write the result to a destination register only if its architectural condition flags satisfy a condition specified in the architectural instruction. A hardware instruction translator translates the instruction into first and second microinstructions. To execute the first microinstruction, an execution pipeline performs the operation on the source operands to generate the result. To execute the second microinstruction, it writes the destination register with the result generated by the first microinstruction if the architectural condition flags satisfy the condition, and writes the destination register with the current value of the destination register if the architectural condition flags do not satisfy the condition.

Abstract: A microprocessor includes a plurality of dynamically reconfigurable functional units, a fingerprint, and a fingerprint unit. As the plurality of dynamically reconfigurable functional units execute instructions according to a first configuration setting, the fingerprint unit accumulates information about the instructions according to a mathematical operation to generate a result. The microprocessor also includes a reconfiguration unit that reconfigures the plurality of dynamically reconfigurable functional units to execute instructions according to a second configuration setting in response to an indication that the result matches the fingerprint.

Abstract: A microprocessor includes a plurality of registers that holds an architectural state of the microprocessor and an indicator that indicates a boot instruction set architecture (ISA) of the microprocessor as either the x86 ISA or the Advanced RISC Machines (ARM) ISA. The microprocessor also includes a hardware instruction translator that translates x86 ISA instructions and ARM ISA instructions into microinstructions. The hardware instruction translator translates, as instructions of the boot ISA, the initial ISA instructions that the microprocessor fetches from architectural memory space after receiving a reset signal. The microprocessor also includes an execution pipeline, coupled to the hardware instruction translator. The execution pipeline executes the microinstructions to generate results defined by the x86 ISA and ARM ISA instructions.

Abstract: A microprocessor includes a plurality of processing cores and an uncore random access memory (RAM) readable and writable by each of the plurality of processing cores. Each core of the plurality of processing cores comprises microcode run by the core that implements architectural instructions of an instruction set architecture of the microprocessor. The microcode is configured to both read and write the uncore RAM to accomplish inter-core communication between the plurality of processing cores.

Abstract: An out-of-order execution microprocessor for reducing the likelihood of having to replay a load instruction due to a store collision. The microprocessor includes a queue of entries, each entry configured to hold information that identifies sources of a store instruction used to compute its store address and to hold a dependency that identifies an instruction upon which the store instruction depends for its data. A register alias table (RAT), coupled to the queue of entries, is configured to encounter instructions in program order and to generate dependencies used to determine when the instructions may execute out of program order. In response to encountering a load instruction the RAT determines whether sources of the load instruction used to compute its load address match the sources of the store instruction in an entry of the queue, and if so, causes the load instruction to share the dependency of the matching store instruction.

Abstract: An architectural instruction instructs a microprocessor to perform an operation on first and second source operands to generate a result and to write the result to a destination register only if architectural condition flags satisfy a condition specified in the architectural instruction. A hardware instruction translator translates the architectural instruction into first and second microinstructions. To execute the first microinstruction, an execution pipeline performs the operation on the source operands to generate the result, determines whether the architectural condition flags satisfy the condition, and updates a non-architectural indicator to indicate whether the architectural condition flags satisfy the condition.

Abstract: A microprocessor includes a predicting unit and a control unit. The control unit controls the predicting unit to accumulate a history of characteristics of executed instructions and makes predictions related to subsequent instructions based on the history while the microprocessor is running a first thread. The control unit also detects a transition from running the first thread to running a second thread and controls the predicting unit to selectively suspend accumulating the history and making the predictions using the history while running the second thread. The predicting unit makes static predictions while running the second thread. The selectivity may be based on the privilege level, identity or length of the second thread, static prediction effectiveness during a previous execution instance of the thread, whether the transition was made due to a system call, and whether the second thread is an interrupt handler.

Abstract: A pipelined out-of-order execution in-order retire microprocessor includes a branch predictor that predicts a target address of a branch instruction, a fetch unit that fetches instructions at the predicted target address, and an execution unit that: resolves a target address of the branch instruction and detects that the predicted and resolved target addresses are different; determines whether there is an unretired instruction that must be corrected and that is older in program order than the branch instruction, in response to detecting that the predicted and resolved target addresses are different; execute the branch instruction by flushing instructions fetched at the predicted target address and causing the fetch unit to fetch from the resolved target address, if there is not an unretired instruction that must be corrected and that is older in program order than the branch instruction; and otherwise, refrain from executing the branch instruction.

Abstract: A data prefetcher in a microprocessor. The data prefetcher includes a plurality of period match counters associated with a corresponding plurality of different pattern periods. The data prefetcher also includes control logic that updates the plurality of period match counters in response to accesses to a memory block by the microprocessor, determines a clear pattern period based on the plurality of period match counters and prefetches into the microprocessor non-fetched cache lines within the memory block based on a pattern having the clear pattern period determined based on the plurality of period match counters.

Abstract: A microprocessor includes a hardware instruction translator that translates an architectural instruction into first and second microinstructions. To execute the first microinstruction, an execution pipeline performs the shift operation on the first source operand to generate the first result and a carry flag value and updates a non-architectural carry flag with the generated carry flag value. To execute the second microinstruction, it performs the second operation on the first result and the second operand to generate the second result and new condition flag values based on the second result. If a architectural condition flags satisfy the condition, it updates the architectural carry flag with the non-architectural carry flag value and updates at least one of the other architectural condition flags with the corresponding generated new condition flag values; otherwise, it updates the architectural condition flags with the current value of the architectural condition flags.

Abstract: A microprocessor includes a hardware instruction translator that translates x86 ISA and ARM ISA machine language program instructions into microinstructions, which are encoded in a distinct manner from the x86 and ARM instructions. An execution pipeline executes the microinstructions to generate x86/ARM-defined results. The microinstructions are distinct from the results generated by the execution of the microinstructions by the execution pipeline. The translator directly provides the microinstructions to the execution pipeline for execution. Each time the microprocessor performs one of the x86 ISA and ARM ISA instructions, the translator translates it into the microinstructions. An indicator indicates either x86 or ARM as a boot ISA. After reset, the microprocessor initializes its architectural state, fetches its first instructions from a reset address, and translates them all as defined by the boot ISA. An instruction cache caches the x86 and ARM instructions and provides them to the translator.

Abstract: An out-of-order execution microprocessor executes an architectural segment register-loading instruction that instructs the microprocessor to load a new value into an architectural segment register of the microprocessor. A comparator compares the new value specified by the architectural segment register-loading instruction with a current contents of the architectural segment register. A control unit causes to be re-executed using the new value all instructions in the microprocessor that used the current architectural segment register contents as a source operand and that are newer in program order than the architectural segment register-loading instruction whenever the comparator indicates the new value does not equal the current contents.

Abstract: A microprocessor includes a first hardware data prefetcher that prefetches data into the microprocessor according to a first algorithm. The microprocessor also includes a second hardware data prefetcher that prefetches data into the microprocessor according to a second algorithm, wherein the first and second algorithms are different. The second prefetcher detects that it is prefetching data into the microprocessor according to the second algorithm in excess of a first predetermined rate and, in response, sends a throttle indication to the first prefetcher. The first prefetcher prefetches data into the microprocessor according to the first algorithm at below a second predetermined rate in response to receiving the throttle indication from the second prefetcher.

Abstract: A microprocessor includes a plurality of processing cores each comprises a corresponding memory physically located inside the core and readable by the core but not readable by the other cores (“core memory”). The microprocessor also includes a memory physically located outside all of the cores and readable by all of the cores (“uncore memory”). For each core, the uncore memory and corresponding core memory collectively provide M words of storage for microcode instructions fetchable by the core as follows: the uncore memory provides J of the M words of microcode instruction storage, and the corresponding core memory provides K of the M words of microcode instruction storage. J, K and M are counting numbers, and M=J+K. The memories are non-architecturally-visible and accessed using a fetch address provided by a non-architectural program counter, and the microcode instructions are non-architectural instructions that implement architectural instructions.

Abstract: A processor includes first and second processing cores configured to support first and second respective subsets of features of its instruction set architecture (ISA) feature set. The first subset is less than all the features of the ISA feature set. The first and second subsets are different but their union is all the features of the ISA feature set. The first core detects a thread, while being executed by the first core rather than by the second core, attempted to employ a feature not in the first subset and, in response, to indicate a switch from the first core to the second core to execute the thread. The unsupported feature may be an unsupported instruction or operating mode. A switch may also be made if the lower performance/power core is being over-utilized or the higher performance/power core is being under-utilized.

Abstract: A data prefetcher in a microprocessor. The data prefetcher includes a plurality of period match counters associated with a corresponding plurality of different pattern periods. The data prefetcher also includes control logic that updates the plurality of period match counters in response to accesses to a memory block by the microprocessor, determines a clear pattern period based on the plurality of period match counters and prefetches into the microprocessor non-fetched cache lines within the memory block based on a pattern having the clear pattern period determined based on the plurality of period match counters.

Abstract: An apparatus for ensuring data coherency within a cache memory hierarchy of a microprocessor during an eviction of a cache line from a lower-level memory to a higher-level memory in the hierarchy includes an eviction engine and an array of storage elements. The eviction engine is configured to move the cache line from the lower-level memory to the higher-level memory. The array of storage elements are coupled to the eviction engine. Each storage element is configured to store an indication for a corresponding cache line stored in the lower-level memory. The indication indicates whether or not the eviction engine is currently moving the cache line from the lower-level memory to the higher-level memory.