Abstract: In a pipelined computer architecture in which instructions may be removed from the instruction queue out of sequence, instruction queue status at a cycle K is determined by adding together the number of invalid instructions or free rows in the queue during cycle K?2, the number of instructions issued for cycle K?1 and the number of instructions speculatively issued in cycle K?1 that have produced a cache hit, and subtracting from the sum the number of instructions enqueued for cycle K?1. The result indicates the number of invalid instructions in the queue cycle K. The number of invalid entries instructions, the number of issued instructions, and the number of enqueued instructions are preferably represented as flat vectors, so that adding is performed by shifting in one direction, while subtracting is performed by shifting in the opposite direction. The result is compared with either the number of instructions to be enqueued in the present cycle, which number is encoded, or with a predetermined value.

Abstract: The present invention relates to a method and apparatus for determining capacitances and charge models for MOS devices to be used in calculating delays in a timing verifier for a circuit. The models are generated by first creating a variety of configurations of MOS devices which vary the inputs to the source, drain, and gate. Such inputs may include rising and falling values as well as constant values at VDD and VSS. Simulations are run on all of the configurations using conditions anticipated for the circuit to be analyzed. Capacitance values obtained from the simulations are used to determine models based upon length and width of the MOS devices using standard curve fitting techniques. Models then can be used for determining delays within the circuit.

Abstract: A technique for managing register assignments. The technique involves maintaining, in a register list memory circuit having entries that respectively correspond to physical registers, a list of register assignments that assign logical registers to the physical registers. The technique further involves maintaining, in a vector memory circuit having bits that respectively correspond to the physical registers, a valid vector that forms, in combination with the list of register assignments, a list of valid register assignments. Furthermore, the technique involves storing, for an instruction that is mapped by the data processor, a copy of the valid vector from the vector memory circuit to a silo memory circuit. Preferably, the processor using the technique has the ability to execute branches of instructions speculatively, and to recover if it is determined that the processor executed down an incorrect instruction branch.

Abstract: A system for accurately determining Elmore delays in DCVSL structures is disclosed. The system uses circuit simulation to determine models for Elmore delays through devices within specific circuit structures. The circuit structures include DCVSL circuits to accurately model performance of devices with such a structure. The system also determines discharge characteristics for DCVSL circuits using simulation. In order to determine Elmore delays, the system analyzes a circuit representation to locate DCVSL structures. The discharge characteristics and models are used to determine Elmore delays for each structure located.

Abstract: The present invention relates to a method and apparatus for determining capacitances and charge models for MOS devices to be used in calculating delays in a timing verifier for a circuit. The models are generated by first creating a variety of configurations of MOS devices which vary the inputs to the source, drain, and gate. Such inputs may include rising and falling values as well as constant values at VDD and VSS. Simulations are run on all of the configurations using conditions anticipated for the circuit to be analyzed. Capacitance values obtained from the simulations are used to determine models based upon length and width of the MOS devices using standard curve fitting techniques. Models then can be used for determining delays within the circuit.

Abstract: In a pipelined computer architecture in which instructions may be removed from the instruction queue out of sequence, instruction queue status at a cycle K is determined by adding together the number of invalid instructions or free rows in the queue during cycle K−2, the number of instructions issued for cycle K−1 and the number of instructions speculatively issued in cycle K−1 that have produced a cache hit, and subtracting from the sum the number of instructions enqueued for cycle K−1. The result indicates the number of invalid instructions in the queue cycle K. The number of invalid entries instructions, the number of issued instructions, and the number of enqueued instructions are preferably represented as flat vectors, so that adding is performed by shifting in one direction, while subtracting is performed by shifting in the opposite direction.

Abstract: In a pipelined computer architecture in which instructions may be removed from the instruction queue out of sequence, instruction queue status at a cycle K is determined by adding together the number of invalid instructions or free rows in the queue during cycle K−2, the number of instructions issued for cycle K−1 and the number of instructions speculatively issued in cycle K−1 that have produced a cache hit, and subtracting from the sum the number of instructions enqueued for cycle K−1. The result indicates the number of invalid instructions in the queue cycle K. The number of invalid entries instructions, the number of issued instructions, and the number of enqueued instructions are preferably represented as flat vectors, so that adding is performed by shifting in one direction, while subtracting is performed by shifting in the opposite direction.

Abstract: The present invention relates to a method and apparatus for determining capacitance and charge models for MOS devices to be used in calculating delays in a timing verifier for a circuit. The models are generated by first creating a variety of configurations of MOS devices which vary the inputs to the source, drain, and gate. Such inputs may include rising and falling values as well as constant values at VDD and VSS. Simulations are run on all of the configurations using conditions anticipated for the circuit to be analyzed. Capacitance values obtained from the simulations are used to determine models based upon length and width of the MOS devices using standard curve fitting techniques. Models then can be used for determining delays within the circuit.

Abstract: A technique for managing register assignments. The technique involves maintaining, in a register list memory circuit having entries that respectively correspond to physical registers, a list of register assignments that assign logical registers to the physical registers. The technique further involves maintaining, in a vector memory circuit having bits that respectively correspond to the physical registers, a valid vector that forms, in combination with the list of register assignments, a list of valid register assignments. Furthermore, the technique involves storing, for an instruction that is mapped by the data processor, a copy of the valid vector from the vector memory circuit to a silo memory circuit. Preferably, the processor using the technique has the ability to execute branches of instructions speculatively, and to recover if it is determined that the processor executed down an incorrect instruction branch.

Abstract: A method and apparatus for determining load capacitance of DCVSL circuits in timing verification of a circuit is disclosed in the present invention. The gate capacitances for various MOS devices are modeled based upon simulations with certain conditions for inputs to the gate, source and drain. The system then determines the existence of DCVSL circuits within the topology of a circuit, and applies one of several models to determine minimum and maximum capacitances for the encountered DCVSL structures. The determination of minimum and maximum capacitance depends upon the selected model and the capacitance of each of the MOS devices as previously calculated.

Abstract: A technique for managing register assignments. The technique involves maintaining, in a register list memory circuit having entries that respectively correspond to physical registers, a list of register assignments that assign logical registers to the physical registers. The technique further involves maintaining, in a vector memory circuit having bits that respectively correspond to the physical registers, a valid vector that forms, in combination with the list of register assignments, a list of valid register assignments. Furthermore, the technique involves storing, for an instruction that is mapped by the data processor, a copy of the valid vector from the vector memory circuit to a silo memory circuit. Preferably, the processor using the technique has the ability to execute branches of instructions speculatively, and to recover if it is determined that the processor executed down an incorrect instruction branch.

Abstract: A technique for managing register assignments. The technique involves maintaining, in a register list memory circuit having entries that respectively correspond to physical registers, a list of register assignments that assign logical registers to the physical registers. The technique further involves maintaining, in a vector memory circuit having bits that respectively correspond to the physical registers, a valid vector that forms, in combination with the list of register assignments, a list of valid register assignments. Furthermore, the technique involves storing, for an instruction that is mapped by the data processor, a copy of the valid vector from the vector memory circuit to a silo memory circuit. Preferably, the processor using the technique has the ability to execute branches of instructions speculatively, and to recover if it is determined that the processor executed down an incorrect instruction branch.

Abstract: A technique for processing register instructions in a pipeline data processor in which multiple instructions may be processed concurrently, and may therefore conflict with one another. Register instructions are identified with register groups indicating which processor registers are affected by the execution of the register instruction. The progress of the execution of the register instruction is then controlled depending upon the identified register groups, in order to avoid conflicts with other concurrently processed instructions.

Abstract: A technique for speculatively issuing instructions using an out-of-order processor. A cache miss by a load instruction results in either a reissue of all subsequently issued instructions for an integer instruction stream, or a reissue of only truly dependent instructions for a floating point instruction stream. One version of the technique involves issuing and executing a first instruction, and issuing a second instruction during a speculative time window of the first instruction that occurs after the first instruction is issued. The technique further involves executing the issued second instruction when the first instruction is executed in a first manner, and reissuing the second instruction and executing the reissued second instruction when the first instruction is executed in a second manner that is different than the first manner.