Abstract: A floating point unit includes a multiplier, an approximation circuit, and a control circuit coupled to the multiplier and the approximation circuit. The approximation circuit is configured to generate an approximation of a difference of the first result from the multiplier and a constant. The control circuit is configured to approximate a function specified by a floating point instruction provided to the floating point unit for execution using an approximation algorithm. The approximation algorithm comprises at least two iterations through the multiplier and optionally the approximation circuit. The control circuit is configured to correct the approximation from the approximation circuit from a first iteration of the approximation algorithm during a second iteration of the approximation algorithm by supplying a correction vector to the multiplier during the second iteration. The multiplier is configured to incorporate the correction vector into the first result during the second iteration.

Abstract: A ROM or other memory may include two or more partitions and a precharge circuit. Each of the partitions may be coupled to separate sets of output conductors, to which the precharge circuit may be coupled. The precharge circuit may precharge the conductors of the partition to be read, while not precharging the other conductors. In one embodiment, the precharge may be to a voltage representing a binary value. In one implementation, the non-precharged conductors may be held to a predetermined voltage different from the voltage to which the precharged conductors are precharged. The predetermined voltage may represent the opposite binary value to the binary value represented by the precharge voltage. The ROM may also include an output circuit which may, in certain embodiments, comprise a logic circuit which logically combines the signals on respective conductors from each partition to provide output signals from the ROM.

Abstract: An apparatus for a processor includes a first scoreboard, a second scoreboard, and a control circuit coupled to the first scoreboard and the second scoreboard. The control circuit is configured to update the first scoreboard to indicate that a write is pending for a first destination register of a first instruction in response to issuing the first instruction into a first pipeline. The control circuit is configured to update the second scoreboard to indicate that the write is pending for the first destination register in response to the first instruction passing a first stage of the pipeline. Replay may be signaled for a given instruction at the first stage. In response to a replay of a second instruction, the control circuit is configured to copy a contents of the second scoreboard to the first scoreboard. In various embodiments, additional scoreboards may be used for detecting different types of dependencies.

Abstract: A processor is described which includes a first pipeline, a second pipeline, and a control circuit. The first pipeline includes a first stage at which instruction results are committed to architected state. The first stage is separated from an issue stage of the first pipeline by a first number of stages. The second pipeline includes a second stage at which an exception is reportable, wherein the second stage is separated from the issue stage of the second pipeline by a second number of stages which is greater than the first number. The control circuit is configured to inhibit co-issuance of a first instruction to the first pipeline and a second instruction to the second pipeline if the first instruction is subsequent to the second instruction in program order.

Abstract: A ROM or other memory may include two or more partitions and a precharge circuit. Each of the partitions may be coupled to separate sets of output conductors, to which the precharge circuit may be coupled. The precharge circuit may precharge the conductors of the partition to be read, while not precharging the other conductors. In one embodiment, the precharge may be to a voltage representing a binary value. In one implementation, the non-precharged conductors may be held to a predetermined voltage different from the voltage to which the precharged conductors are precharged. The predetermined voltage may represent the opposite binary value to the binary value represented by the precharge voltage. The ROM may also include an output circuit which may, in certain embodiments, comprise a logic circuit which logically combines the signals on respective conductors from each partition to provide output signals from the ROM.

Abstract: An apparatus for a multiplexor circuit includes a passgate circuit coupled to receive input signals and corresponding select signals comprising a subset of the input signals and select signals received by the multiplexor. The apparatus also includes a default circuit coupled to receive the select signals and coupled to an output node of the passgate circuit. If none of the select signals is asserted, the default circuit supplies a default voltage on the output node. Other passgate circuits and default circuits may be included coupled to other subsets of the input signals and select signals, and an output circuit may be included with inputs coupled to the output nodes of the passgate circuits. The default voltage may represent a logical value which allows the value from another passgate circuit to control the output of the output circuit.

Abstract: A ROM or other memory may include two or more partitions and a precharge circuit. Each of the partitions may be coupled to separate sets of output conductors, to which the precharge circuit may be coupled. The precharge circuit may precharge the conductors of the partition to be read, while not precharging the other conductors. In one embodiment, the precharge may be to a voltage representing a binary value. In one implementation, the non-precharged conductors may be held to a predetermined voltage different from the voltage to which the precharged conductors are precharged. The predetermined voltage may represent the opposite binary value to the binary value represented by the precharge voltage. The ROM may also include an output circuit which may, in certain embodiments, comprise a logic circuit which logically combines the signals on respective conductors from each partition to provide output signals from the ROM.

Abstract: A leading one correction circuit receives a significand from a floating point adder and a corresponding leading one prediction from a leading one predictor, and determines if the leading one prediction is correct. In one embodiment, the leading one prediction is a one hot vector having the same number of bits as the significand, with the set bit in the position predicted to have the leading one. In such an embodiment, the leading one correction circuit may perform a bitwise AND of the significand and leading one prediction, and the result of the bitwise AND may be ORed to generate a signal indicating whether or not the prediction is correct. In one implementation, the leading one correction circuit may operate concurrent with a shift of the significand in response to a shift amount indicated by the leading one prediction.

Abstract: A ROM or other memory may include two or more partitions and a precharge circuit. Each of the partitions may be coupled to separate sets of output conductors, to which the precharge circuit may be coupled. The precharge circuit may precharge the conductors of the partition to be read, while not precharging the other conductors. In one embodiment, the precharge may be to a voltage representing a binary value. In one implementation, the non-precharged conductors may be held to a predetermined voltage different from the voltage to which the precharged conductors are precharged. The predetermined voltage may represent the opposite binary value to the binary value represented by the precharge voltage. The ROM may also include an output circuit which may, in certain embodiments, comprise a logic circuit which logically combines the signals on respective conductors from each partition to provide output signals from the ROM.

Abstract: A circuit for stalling data in a domino pipeline. The circuit includes a logic network having multiple inputs coupled to receive multiple input data signals. The logic network generates an output signal on an output node based on a logic evaluation of the multiple input data signals. The circuit also includes a feedback circuit coupled to the logic network to maintain the output signal on the output node based on a stall input signal.