Abstract: A computer architecture to process load instructions by allowing multiple mappings between logical registers and the same physical register is disclosed. The computer architecture includes a processor having a physical registers. The processor also includes a decoder to decode a load instruction that names a destination logical register. The processor also includes a register allocation table to map the destination logical register to a physical register within the plurality of physical registers. If the load instruction is predicted to collide with a prior load instruction that names a destination logical register, then the register allocation table maps the destination logical register to the physical register allocated to the first load instruction.

Abstract: A system and corresponding method use a PAUSE instruction as a low power hint in a single threaded or multithreaded environment using “processor slow mode.” One embodiment actually lowers the frequency of the processor clock. Another embodiment virtually lowers the frequency of the processor clock by gating M clock cycles out of every N clock cycles. When all threads have issued a PAUSE instruction, the processor enters slow mode and remains there for a while. After this while, the processor returns to normal mode. Alternatively, an event, such as an interrupt or an exception, can cause the processor to return to normal mode from slow mode.

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 producing a fused instruction is described. In one embodiment, a first instruction and a second instruction that are both simple instructions (e.g., perform only one operation) and are dependent are fused together to create the fused instruction. The fused instruction has an opcode that represents the operation performed by the first instruction and the operation performed by the second instruction. The fused instruction has three source operands and one destination operand. Two of the three source operands are the two source operands of the first instruction, and the third source operand is the source operand of the second instruction that is not the destination operand of the first instruction. The destination operand of the fused instruction is the destination operand of the second instruction. An execution unit that can execute a fused instruction in one clock cycle is also disclosed.

Abstract: A system and method for recovering from mispredicted paths in pipelined computer architectures. Targets within an instruction window exhibit spatial locality. To exploit this property, a mechanism detects the branch target within the instruction window. A second process eliminates the need for full renaming and re-execution of mispredicted paths by handling a dependency chain of instructions.

Abstract: Apparatus and methods to track a register value. A microprocessor can include a first register, a control circuit, and an adder. The first register can store a tracked register value. The control circuit can include an instruction input to receive at least a portion of an instruction and a first output to output an arithmetic operation indication. The adder can include a control input to receive the arithmetic operation indication, a first input to receive an immediate operand of an instruction, and a second input to receive the tracked register value.

Abstract: The present invention is directed to a computer system and method for early resolution of a set of critical instructions. The computer system may include a scoreboard, a scheduling window and a confidence predictor. The scoreboard may include a set of reservation stations. Each one of the set of reservation stations may correspond to one of a set of decoded instructions. Each one of the set of reservation stations may have a priority field. The scheduling window may maintain the scoreboard, wherein if one of the set of decoded instructions is one of the set of critical instructions, the scheduling window may mark the priority field corresponding to the particular one of the set of decoded instructions and also may find and mark the priority field of each of a set of base instructions upon which the particular one of the set of decoded instructions depends. The confidence predictor may also be used to predict whether one of the set of decoded instructions is one of the set of critical instructions.

Abstract: According to one aspect of the invention, a method is provided in which a current instance of an instruction is received. The current instance of the instruction contains a reference to a logical floating point register. A first rename phase is performed to convert the current's instance reference to the logical floating point register into a reference to an absolute register. A second rename phase is performed in parallel with the first rename phase to convert the reference to the absolute register into a reference to a physical register, based upon results obtained from performing the first rename phase with respect to a previous instance of the instruction.

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

Abstract: A system and corresponding method use a PAUSE instruction as a low power hint in a single threaded or multithreaded environment using “processor slow mode.” One embodiment actually lowers the frequency of the processor clock. Another embodiment virtually lowers the frequency of the processor clock by gating M clock cycles out of every N clock cycles. When all threads have issued a PAUSE instruction, the processor enters slow mode and remains there for a while. After this while, the processor returns to normal mode. Alternatively, an event, such as an interrupt or an exception, can cause the processor to return to normal mode from slow mode.

Abstract: A computer architecture to process load instructions by allowing multiple mappings between logical registers and the same physical register is disclosed. The computer architecture includes a processor having a physical registers. The processor also includes a decoder to decode a load instruction that names a destination logical register. The processor also includes a register allocation table to map the destination logical register to a physical register within the plurality of physical registers. If the load instruction is predicted to collide with a prior load instruction that names a destination logical register, then the register allocation table maps the destination logical register to the physical register allocated to the first load instruction.

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: Method for producing a predetermined length page memory pointer record, according to a selected page size and a selected page address, the method including the procedures of: determining a dynamic location of a separator bit within the page memory pointer record, according to the selected page size and an initial page size, the initial page size being respective of the smallest page size in a given memory system, writing a predetermined value to the dynamic location, writing a sequence of values opposite to the predetermined value to selected page size bits of the page memory pointer record, when the selected page size is different than the initial page size, and writing the selected page address to selected page address bits of the page memory pointer record.

Abstract: A system and method for producing a fused instruction is described. In one embodiment, a first instruction and a second instruction that are both simple instructions (e.g., perform only one operation) and are dependent are fused together to create the fused instruction. The fused instruction has an opcode that represents the operation performed by the first instruction and the operation performed by the second instruction. The fused instruction has three source operands and one destination operand. Two of the three source operands are the two source operands of the first instruction, and the third source operand is the source operand of the second instruction that is not the destination operand of the first instruction. The destination operand of the fused instruction is the destination operand of the second instruction. An execution unit that can execute a fused instruction in one clock cycle is also disclosed.

Abstract: A method and apparatus for executing low power validations for high confidence predictions. More particularly, the present invention pertains to using confidence levels of speculative executions to decrease power consumption of a processor without affecting its performance. Non-critical instructions, or those instructions whose prediction, rather than verification, lie on the critical path, can thus be optimized to consume less power.

Abstract: Method for producing a predetermined length page memory pointer record, according to a selected page size and a selected page address, the method including the procedures of: determining a dynamic location of a separator bit within the page memory pointer record, according to the selected page size and an initial page size, the initial page size being respective of the smallest page size in a given memory system, writing a predetermined value to the dynamic location, writing a sequence of values opposite to the predetermined value to selected page size bits of the page memory pointer record, when the selected page size is different than the initial page size, and writing the selected page address to selected page address bits of the page memory pointer record.

Abstract: Method for producing a predetermined length page memory pointer record, according to a selected page size and a selected page address, the method including the procedures of: determining a dynamic location of a separator bit within the page memory pointer record, according to the selected page size and an initial page size, the initial page size being respective of the smallest page size in a given memory system, writing a predetermined value to the dynamic location, writing a sequence of values opposite to the predetermined value to selected page size bits of the page memory pointer record, when the selected page size is different than the initial page size, and writing the selected page address to selected page address bits of the page memory pointer record.

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 method for dynamically controlling the population size of confidence assignments to which confidence level predictions are assigned. The method includes comparing a confidence level prediction and a threshold indication to generate a confidence assignment. The confidence assignment is used to generate another threshold indication. The threshold indication is dynamically adjusted so as to control the population size of confidence assignments to which confidence level predictions are assigned.

Abstract: A computer architecture for collapsing dependency graphs for colliding store and load instructions. Many-to-one mappings are provided between logical registers and physical registers, so that more than one logical register may map to the same physical register. For a load instruction that is predicted to collide with an earlier in-flight store instruction, the destination logical register of the load instruction is mapped to the same physical register to which the source logical register of the earlier in-flight store instruction is mapped. A many-to-one mapping may be realized by associating a counter with each physical register, so that the value of a counter indicates whether its associated physical counter is free.