Abstract: The present invention is directed to an apparatus and method for data collapsing based on control-flow speculation (conditional branch predictions). Because conditional branch outcomes are resolved based on actual data values, the conditional branch prediction provides potentially valuable insight into data values. Upon encountering a branch if equal instruction and this instruction is predicted as taken or a branch if not equal instruction and this instruction is predicted as not taken, this invention assumes that the two operands used to determine the conditional branch are equal. The data predictions are safe because a data misprediction means a conditional branch misprediction which results in a pipeline flush of the instructions following the conditional branch instruction including the data mispredictions.

Abstract: A system and method for predicting a branch target for a current instruction in a microprocessor, the system comprising a cache storing indirect branch instructions and a path register. The path register is updated on certain branches by an XOR operation on the path register and the branch instruction, followed by the addition of one or more bits to the register. The cache is indexed by performing an operation on a portion of the current instruction address and the path register; the entry returned, if any, may be used to predict the target of the current instruction.

Abstract: A device is presented including a processor. A local memory is connected to the processor. The processor includes a hot way cache accessing process. A method is presented that includes accessing a memory. The method includes processing a first plurality of memory cells and a second plurality of memory cells in the memory. The method determines if a memory block is a last recently accessed memory block. The method determines whether a memory block accessed is a hit or a miss. The method accesses a lower memory level if the memory block accessed is a miss. Also, processing the second plurality of memory cells for an exact block if the block accessed is a hit but not the last recently accessed memory block. And, providing the memory block for additional access if the memory block accessed is a hit and is a last recently accessed memory block.

Abstract: Apparatus and methods to filter memory record updates. A microprocessor can include a memory record update filter. The memory record update filter can include a table memory populated by a plurality of data entries. Each data entry can include a data tag field to store a data tag, a data field to store a data value, and a filter field to store a filter value. A first comparator can be in communication with the data tag field of the table memory and a data accessing information input to perform a data tag comparison. A second comparator can be in communication with the filter field of the table memory and a data value input. A control circuit can be in communication with the table memory, the first comparator, and the second comparator.

Abstract: In an enhanced virtual renaming scheme within a processor, multiple logical registers may be mapped to a single physical register. A value cache determines whether a new value generated pursuant to program instructions matches values associated with previously executed instructions. If so, the logical register associated with the newly executed instruction shares the physical register. Also, deadlock preventatives measures may be integrated into a register allocation unit in a manner that “steals” a physical register from a younger executed instruction when a value from an older instruction is generated-in a processor core.

Abstract: A computer architecture to process move instructions by allowing multiple mappings between logical registers and the same physical register. In one embodiment, a counter is associated with each physical register to indicate when the physical register is free. A register-to-register move instruction is processed by mapping the logical destination register of the move instruction to the same physical register to which the logical source register of the move instruction is mapped. An immediate-to-register move instruction is processed by mapping the logical destination register of the move instruction to a physical register storing the immediate.

Abstract: A cache architecture is adapted to store data items of variable length. Given appropriate circumstances, the cache architecture permits multiple data items to be retrieved from the cache in single clock cycle. The cache architecture may find application in a front end processing system of a processor storing instruction segments. If a first instruction segment does not occupy the full width of the cache, other instruction segments can be retrieved from the cache simultaneously with the first instruction segment. The cache may be organized into a plurality of cache banks, each cache bank being independently addressed. Each bank may consist of several cache ways.

Abstract: A processor system and method that reduces the number of register value copying made from alias registers to corresponding real (architectural) registers. The method entails determining whether to copy the register value generated by executing an instruction from the alias register to the real register at the time the reorder buffer entry associated with the alias register is needed for a new instruction. If before the reorder buffer is needed for a new instruction, an interim instruction resulted in a new register value for the real register, then the original register value would be invalid at the time the reorder buffer entry is needed for the new instruction. Thus, there would not be a need to copy the original register value to the real register. The reduction in copying can make the processor system consume less power.

Abstract: A system is described that includes a microprocessor and a thermal control subsystem. The microprocessor includes execution resources to support processing of instructions and consumes power. The microprocessor also includes at least one throttling mechanism to reduce the amount of heat generated by the microprocessor. The thermal control subsystem is configured to estimate an amount of power used by the microprocessor and to control the throttling mechanism based on the estimated amount of current power usage to ensure that junction temperature will not exceed the maximum allowed temperature.

Abstract: A processor system and method that reduces the number of register value copying made from alias registers to corresponding real (architectural) registers. One method entails not performing an alias register to real register copying if the incoming instruction does not designate a real register. Another method entails delaying alias register to real register copying until the corresponding reorder buffer (ROB) entry is actually written to. Yet another method entails not performing an alias register to real register copying if the ROB entry is the same as the existing ROB entry. And, still another method entails further delaying or stalling the allocation of an ROB entry.

Abstract: Distribution of processing activity across processing hardware based on power consumption and/or thermal considerations. One embodiment includes a plurality of processing units and a monitor to obtain monitor (e.g., power consumption, or temperature or some combination thereof) values from the processing units. The monitor transfers a process from one processing unit to another in response to the monitor values from the processing units.

Abstract: Apparatus and methods to filter memory record updates. A microprocessor can include a memory record update filter. The memory record update filter can include a table memory populated by a plurality of data entries. Each data entry can include a data tag field to store a data tag, a data field to store a data value, and a filter field to store a filter value. A first comparator can be in communication with the data tag field of the table memory and a data accessing information input to perform a data tag comparison. A second comparator can be in communication with the filter field of the table memory and a data value input. A control circuit can be in communication with the table memory, the first comparator, and the second comparator.

Abstract: In an enhanced virtual renaming scheme within a processor, multiple logical registers may be mapped to a single physical register. A value cache determines whether a new value generated pursuant to program instructions matches values associated with previously executed instructions. If so, the logical register associated with the newly executed instruction shares the physical register. Also, deadlock preventatives measures may be integrated into a register allocation unit in a manner that “steals” a physical register from a younger executed instruction when a value from an older instruction is generated in a processor core.

Abstract: A cache architecture is adapted to store data items of variable length. Given appropriate circumstances, the cache architecture permits multiple data items to be retrieved from the cache in single clock cycle. The cache architecture may find application in a front end processing system of a processor storing instruction segments. If a first instruction segment does not occupy the full width of the cache, other instruction segments can be retrieved from the cache simultaneously with the first instruction segment. The cache may be organized into a plurality of cache banks, each cache bank being independently addressed. Each bank may consist of several cache ways.

Abstract: Power conservation may be achieved in a front end system by disabling a segment builder unless program flow indicates a sufficient likelihood of segment reuse. Power normally spent in collecting decoded instructions, detecting segment beginning and end conditions and storing instruction segments is conserved by disabling those circuits that perform these functions. An access filter may maintain a running count of the number of times instructions are read from an instruction cache and may enable the segment construction and storage circuits if the running count meets or exceeds a predetermined threshold.

Abstract: A memory cache bank prediction unit is provided for use in a processor having a plurality of memory cache banks. The memory cache bank prediction unit has an input port that receives an instruction. The memory cache bank prediction unit also has an evaluation unit, coupled to the input port, that predicts which of the plurality of memory cache banks is associated with the instruction.

Abstract: A system and method for predicting a branch target for a current instruction in a microprocessor, the system comprising a cache storing indirect branch instructions and a path register. The path register is updated on certain branches by an XOR operation on the path register and the branch instruction, followed by the addition of one or more bits to the register. The cache is indexed by performing an operation on a portion of the current instruction address and the path register; the entry returned, if any, may be used to predict the target of the current instruction.

Abstract: The present invention is directed to an apparatus and method for data collapsing based on control-flow speculation (conditional branch predictions). Because conditional branch outcomes are resolved based on actual data values, the conditional branch prediction provides potentially valuable insight into data values. Upon encountering a branch if equal instruction and this instruction is predicted as taken or a branch if not equal instruction and this instruction is predicted as not taken, this invention assumes that the two operands used to determine the conditional branch are equal. The data predictions are safe because a data misprediction means a conditional branch misprediction which results in a pipeline flush of the instructions following the conditional branch instruction including the data mispredictions.

Abstract: A device is presented including a processor. A local memory is connected to the processor. The processor includes a hot way cache accessing process. A method is presented that includes accessing a memory. The method includes processing a first plurality of memory cells and a second plurality of memory cells in the memory. The method determines if a memory block is a last recently accessed memory block. The method determines whether a memory block accessed is a hit or a miss. The method accesses a lower memory level if the memory block accessed is a miss. Also, processing the second plurality of memory cells for an exact block if the block accessed is a hit but not the last recently accessed memory block. And, providing the memory block for additional access if the memory block accessed is a hit and is a last recently accessed memory block.

Abstract: A power aware front-end unit for a processor may include a UOP cache that disables other circuitry within the front-end unit. In an embodiment, a front-end unit may disable instruction synchronization circuitry, instruction decode circuitry and, optionally, instruction fetch circuitry while instruction look-ups are underway in both a block cache and an instruction cache. If the instruction look-up indicates a miss, the disabled circuitry thereafter may be enabled.