Hewlett-packard Development Company, L.P.

Hewlett-packard Company

Barry Joseph Arnold

Russell C Brockmann

Stephen R Undy

James Earl McCormick, Jr

James Curtis Stout

Anuj Dua

Kevin M Laake

Andrew R Allen

David Carl Kubicek

Samuel D Naffziger

Glenn T Colon-Bonet

Don D Josephson

Kenneth Koch, Ii

Thomas Justin Sullivan

Philip L Barnes

Nicholas Albert Michell

Navin Amar Ghisiawan

Dacheng (Henry) Zhou

Mike Griffith

A data clock recovery system is provided. A phase detector is configured to sample an input data stream by way of a data clock and a second clock to generate a first signal indicating whether a data clock lags or leads a preferred phase of the data clock in relation to an input data stream. A phase controller is configured to process the first signal to shift a phase of the second clock toward a second preferred phase, and to shift a phase of the data clock toward the first preferred phase after the shifting of the phase of the second clock.

Data clock recovery system and method employing delayed data clock phase shifting

Systems and methods for driving data over a data bus are disclosed. One embodiment of a system may comprise a bus clock signal that is a copy of a system clock signal that controls the timing associated with transferring data over the bus, a data clock signal that is designed to lead the system clock by a portion of a clock cycle to drive data over the bus ahead of the bus clock signal, an output latch device that drives data over the data bus in response to an edge of the data clock signal and a skew corrector that mitigates racing of data over the data bus in the event that the data clock lags the bus clock.

Systems and methods for driving data over a bus where the systems employ a bus clock that is derived from a system clock and a data clock designed to lead the bus clock

Systems and methods of reducing bus turnaround time in a multiprocessor architecture are disclosed. An exemplary method may include mastering the system bus within one idle bus clock cycle of a bus handoff. The method may also include bypassing data from recovery latches and instead receiving data from pipeline latches into core logic, the received data mirroring data driven onto the system bus.

Reduced bus turnaround time in a multiprocessor architecture

A method of, and apparatus for, interfacing the hardware of a processor capable of processing instructions from more than one type of instruction set. More particularly, an engine responsible for fetching native instructions from a memory subsystem (such as an EM fetch engine) is interfaced with an engine that processes emulated instructions (such as an x86 engine). This is achieved using a handshake protocol, whereby the x86 engine sends an explicit fetch request signal to the EM fetch engine along with a fetch address. The EM fetch engine then accesses the memory subsystem and retrieves a line of instructions for subsequent decode and execution. The EM fetch engine sends this line of instructions to the x86 engine along with an explicit fetch complete signal. The EM fetch engine also includes a fetch address queue capable of holding the fetch addresses before they are processed by the EM fetch engine. The fetch requests are processed such that more than one fetch request may be pending at the same time. If a pending fetch request is canceled due to a pipeline flush, then the fetch address queue is cleared and the pending fetch requests are canceled. The system also prevents macroinstruction (MIQ)-related stalls by using a speculative write pointer to control the issuance of fetch requests, thereby preventing the MIQ from becoming oversubscribed.

Method and apparatus for fetching instructions from the memory subsystem of a mixed architecture processor into a hardware emulation engine

A signal generated by circuitry for an output buffer is identified relative to a clock signal to control a slew rate of the circuitry for an output buffer.

Output buffer slew rate control using clock signal

One disclosed method comprises drawing current from a termination voltage supply and through a termination voltage delivery network by termination circuitry in response to a first signal on one or more lines terminated by the termination circuitry, shunting current from the termination voltage supply and through the termination voltage delivery network in response to a second signal on one or more terminated lines, and helping to reduce the shunted current for extended shunting.

Shunted current reduction

An integrated circuit is configured as a selected one of a terminated and a non-terminated bus agent for terminating a bus signal line. Reference level selection logic selects one of a first and a distinct second reference level as a selected level. The integrated circuit compares the bus signal line with the selected level to determine the state of the bus signal line.

Bus agent having multiple reference levels

An apparatus includes termination circuitry to terminate one or more lines. The termination circuitry draws a first current from a termination voltage supply through a termination voltage delivery network for each terminated line carrying a first signal. Partial current shunt circuitry draws a second current from the termination voltage supply through the termination voltage delivery network for each terminated line carrying a second signal. The first and second currents are distinct.

Partial termination voltage current shunting

One or more characteristics of circuitry for an output buffer are identified relative to a reference a plurality of times to produce a sequence of results. One or more compensation signals for one or more output buffers are generated based on results satisfying one or more conditions.

Output buffer compensation control

An embodiment of this invention provides a circuit and method for improving the testability of I/O driver/receivers. First, two separate I/O driver/receiver pads are electrically connected. A bit pattern generator in one of the I/O driver/receivers drives a bit pattern through a driver to the connected pads. The bit pattern is then driven through the receiver of a second I/O driver/receiver to a first clocked register. An identical bit pattern generator in the second I/O driver/receiver then drives an identical bit pattern into a second clocked register. A comparator compares the outputs of these two registers. If the two bit patterns don't match, the comparator signals there is a functional problem with one of the I/O driver/receivers.

Method and apparatus for improving testability of I/O driver/receivers

Termination circuitry is to terminate one or more lines and is to draw current from a termination voltage supply and through a termination voltage delivery network. Partial termination voltage current shunting may be used to help define a range of current variation through the termination voltage delivery network.

Circuitry for scanning and observing domino CMOS logic or other logic gates. Master and slave stages includes circuitry for latching a bit into the master stage through pulsing of a clock signal and subsequently latching the bit into the slave stage through pulsing of another clock signal. The number of transistors required for scanning is minimized by using existing latch structures within the logic.

Method for adding scan controllability and observability to domino CMOS with low area and delay overhead

A logic circuit includes a dynamic logic stage driving a dynamic evaluation stage. The dynamic logic stage responds to input signals and a clock wave to derive an output signal that is a logic function of the input signals. The output signal is derived only during a first portion of each cycle of the clock wave. The evaluation stage responds to the output signal only during an initial segment of the first portion of each clock wave cycle.

Dynamic logic circuit

A driver circuit for capacitively loaded lines. The driver circuit has both precharge/pull-low and hold-high. The capacitively loaded line is precharged during a precharge phase of a clock signal. The driver circuit is active only during a drive phase of a clock signal. The driver has a hold-up transistor that is sufficiently large to suppress noise coupled into the line during the drive phase, but is substantially smaller than what is required to make pull-up time equal to pull-down time. The driver circuit provides the low noise characteristics of push-pull but with less circuit area and line capacitance than typical push-pull driver circuits.

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Fort Collins, CO, United States of America

Barry Joseph Arnold