Hewlett-packard Development Company, L.p.

Compaq Computer Corporation, Inc.

Timothy Charles Fischer

Samuel D Naffziger

Daniel Lawrence Leibholz

James Arthur Farrell

Benjamin James Patella

Derrick R Meyer

Bruce Alan Gieseke

Charles Corey Pie

Sharon Marie Britton

Sven Eric Meier

Daming Jin

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&#x2212;2, the number of instructions issued for cycle K&#x2212;1 and the number of instructions speculatively issued in cycle K&#x2212;1 that have produced a cache hit, and subtracting from the sum the number of instructions enqueued for cycle K&#x2212;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. A stall signal is generated if the indicative value is less than the encoded number or the predetermined value.

Method and circuits for early detection of a full queue

One embodiment of the invention comprises, in each clock zone of a central processing unit, at least one sensor that generates a power signal indicative of a power supply voltage within the clock zone, a clock generator for providing a variable frequency clock to the clock zone, and a controller for controlling an operating frequency of the clock generator in response to the power signal and in response to frequency adjustment communications from other clock zones.

Central processing unit with multiple clock zones and operating method

Systems and methods of edge calibration for synchronous data transfer between clock domains are disclosed. An exemplary method may comprise comparing a drive clock signal to a receive clock signal, generating a select clock signal, and configuring a data path based a least in part on the select clock signal for synchronous data transfer between clock domains so that data arrives in an early clock domain at the desired logical clock cycle.

Edge calibration for synchronous data transfer between clock domains

Systems and methods for implanting synchronous data transfer between clock domains are disclosed. An exemplary system may comprise an adaptable data path having an input for receiving a signal from a first clock domain and an output in a second clock domain. A controller is operatively associated with the adaptable data path. The controller is responsive to operating parameters to configure the adaptable data path to align a logical clock pulse on the signal received from the first clock domain with the same logical clock pulse in the second clock domain based on a measured delay between the first and second clock domains.

Adaptable data path for synchronous data transfer between clock domains

Systems and methods for implementing count calibration for synchronous data transfer between clock domains are disclosed. An exemplary system may include a count calibration circuit for determining latency between an early clock domain and a late clock domain. The system may also include a data path configurable for synchronous data transfer between clock domains based at least in part on the latency.

Count calibration for synchronous data transfer between clock domains

In one embodiment, a central processing unit (CPU) includes multiple clock zones. Each clock zone includes at least one sensor that generates a signal indicative of a power supply voltage within the clock zone, a clock generator for providing a variable frequency clock to the clock zone, a first controller for controlling a frequency of operation of the clock generator in response to the at least one sensor, wherein the first controller further controls the frequency of operation in response to communication of frequency adjustments from first controllers in other clock zones within one cycle of latency, and a second controller that provides an overdrive signal, that is combined with adjustment signals from the first controller for the clock generator, in response to communication of frequency adjustments from other clock zones beyond one cycle of latency.

System and method for synchronizing multiple variable-frequency clock generators

In a preferred embodiment, the invention provides a method and system for allowing a frequency synthesizer to function despite long delays. A first and second phase comparator, each with at least three inputs and an output are preset to a predetermined logical value by a first control circuit. A first signal is connected to an input of the first and second phase comparators. A second signal is connected to a second input of the second phase comparator and to the input of a programmable dead zone delay circuit. The output of the programmable dead zone delay circuit is connected to a second input of the first phase comparator. A preset value, determined by the first control circuit, is presented on the outputs of the first and second phase comparators. Until metastability is resolved, these outputs retain a valid fail-safe default.

Method and system for fail-safe control of a frequency synthesizer

A method of compacting an instruction queue in an out of order processor includes determining the number of invalid instructions below and including each row in the queue, by counting invalid bits or validity indicators associated with rows below and up to the current row. For each row, multiplexor select signals are generated from the flat vector counts for the N rows above and including the present row, and from the validity indicators associated with the N rows, where N is a predetermined value. A multiplexor associated with a particular row selects one of the N rows according to the select value, and moves or passes the instruction held in the selected row to the present row. A row's select value is determined by forming a diagonal from the N count vectors corresponding to the N rows above and including the present row, and logically ANDing, each diagonal bit with the valid bit associated with the same row. Each row's count vector is determined in two stages. In the first stage, a local count is determined for each row in a local group of rows, and a global count is determined for the entire local group. Each local count is determined by counting the validity indicators associated with rows in the local group. In the second stage, a final count is determined for each row in the queue, by combining the local and global counts generated for the local group in the first stage, with global counts generated in local groups below the local group. The N rows can extend to the queue's input pipeline.

Method for compacting an instruction queue

A computer hardware system is disclosed for determining during a single clock cycle whether a data buffer having a plurality of entries can accept additional data. The system has multiple stages, having one or more adders/encoders that process the data buffer entries' valid bits in parallel. Groups of entries are associated with first-stage adders/encoders. Valid bits and their complements for entries in each group are received into multiple first-stage adders that compute and output encoded values indicating the number of available entries within each group, or first-stage totals. The adders also encode the first-stage totals such that a saturated count corresponds to a pre-charged state of the first-stage adder. The first-stage totals are then sent to additional stages having adders/encoders that are substantially the same as the first-stage adders/encoders. The additional-stage adders combine the encoded totals from prior stages and determine whether the buffer has available entries.

System and method for checking bits in a buffer with multiple entries

The present invention is directed to a method for evaluating a circuit design to identify potential race conditions including the steps of identifying switching elements in a design, storing control node and switched node pair information for each of the switching elements, identifying stacks of the switching elements; storing information about the stacks of switching elements; identifying parallel connected ones of the switching elements; identifying parallel stacks; and calculating a combined switching current for the parallel switching elements and stacks.

Method and apparatus for identifying switching race conditions in a circuit design

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&minus;2, the number of instructions issued for cycle K&minus;1 and the number of instructions speculatively issued in cycle K&minus;1 that have produced a cache hit, and subtracting from the sum the number of instructions enqueued for cycle K&minus;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. A stall signal is generated if the indicative value is less than the encoded number or the predetermined value

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.

Technique for ordering internal processor register accesses

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.

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Firestone, CO, United States of America

Timothy Charles Fischer