International Business Machines Corporation

Apple Inc.

Raymond Cheung Yeung

Dung Q Nguyen

Hung Qui Le

Michael K Gschwind

Brian William Thompto

Robert Alan Philhower

Balaram Sinharoy

William Elton Burky

James Wilson Bishop

Eric M Schwarz

Alper Buyuktosunoglu

Pradip Bose

Ravi Nair

Michael R Seningen

Chen-Yong Cher

Juergen Haess

Robert D Kenney

Michael Klaus Kroener

Paul K Miller

Lawrence Joseph Powell, Jr

Wolfram Sauer

Mark H Nodine

Son Dao-Trong

Donald W Glowka

Jeffrey B Reed

Asit S Ambekar

Lincoln R Nunes

Irfan Waheed

Geoffrey F Oh

A funnel shifter includes an input, an output, and a multiplexer unit including a number of multiplexer levels. The multiplexer unit may perform one of a plurality of shift operations on an input value and to provide an output value in response to receiving a shift value and a shift operation value. A first multiplexer level may be configured to format and expand the input value into a larger intermediate value. At least a second multiplexer level may be configured to perform a linear shift of the intermediate value without wrapping any bits for creating the output value. At least some of the multiplexer levels may include multiplexer select signals that may be represented as a plurality of N-Nary one of N signals where N is greater than or equal to two, wherein each of the plurality of N-Nary signals being implemented on a set of physical wires.

Funnel shifter implementation

A one-of-n storage cell for use in an N-nary dynamic logic (NDL) circuit. The storage cell may accept an input value and provide a complemented output value that corresponds to the input value. However, if an input value that corresponds to a precharge input value is received, the output value remains the previous output value. The storage cell may be implemented to accept either inverted or non-inverted one-of-n NDL signals and to provide as an output either non-inverted or inverted one-of-N NDL signals, respectively, where N is greater than two.

One-of-n N-nary logic implementation of a storage cell

A method for preparing an IC design that has been modified to be formally verified with a reference IC design. Because some formal verification tools cannot handle the complexity often associated with sequential equivalence checking at the top level of a circuit, the modified IC design may be instantiated into a number of different design versions, each having different levels of modification complexity. In addition, the reference IC design and the modified versions may be decomposed into a datapath and control path. The reference IC design and each of the modified IC design versions may also use wrappers to encapsulate various levels of hierarchy of the logic. Lastly, rather than having to verify each of the modified versions back to the reference IC design, the equivalence checking may be performed between each modified IC design version and a next modified IC design version having a greater modification computational complexity.

Method for preparing for and formally verifying a modified integrated circuit design

A method, apparatus, and computer program product are disclosed for ensuring processing fairness in simultaneous multi-threading (SMT) microprocessors. A clock cycle priority is assigned to a first thread and to a second thread during a standard selection state that lasts for an expected number of clock cycles by selecting the first thread to be a primary thread and the second thread to be a secondary thread. If a condition exists that requires overriding, an override state is executed by selecting the second thread to be the primary thread and the first thread to be the secondary thread. The override state is forced to be executed for an override period of time which equals the expected number of clock cycles plus a forced number of clock cycles. The forced number of clock cycles is granted to the first thread in response to the first thread again becoming the primary thread.

Thread priority method for ensuring processing fairness in simultaneous multi-threading microprocessors

A hardware description language representation of an original circuit block containing one or more hierarchies may be obtained. Some, or all of the hierarchies may be dissolved to access each circuit component within the original circuit block at a same level of hierarchy. Designated circuit components may then be grouped together to create new circuit blocks at a new level of hierarchy. Components and signals within each new circuit block may be renamed to match logically corresponding components and signals within each other new circuit block. Missing pins may be added for each new circuit block, and connected to respective associated signals within the new circuit block, and logically equivalent pins may be given the same name to ensure the new circuit blocks are logically equivalent to each other and have identical interfaces. One of the new circuit blocks may be selected for physical build to obtain one or more physical instances corresponding to the selected new circuit block, and a top-level build may link each new circuit block instance to one of those one or more physical instances.

Method for manipulating and repartitioning a hierarchical integrated circuit design

An information handling system employs a processor that includes a thread priority controller. An issue unit in the processor sends branch issue information to the thread priority controller when a branch instruction of an instruction thread issues. In one embodiment, if the branch issue information indicates low confidence in a branch prediction for the branch instruction, the thread priority controller speculatively increases or boosts the priority of the instruction thread containing this low confidence branch instruction. In the manner, should a branch redirect actually occur due to a mispredict, a fetcher is ready to access a redirect address in a memory array sooner than would otherwise be possible.

Method and apparatus for thread priority control in a multi-threaded processor based upon branch issue information including branch confidence information

An information handling system includes a processor that throttles an instruction fetcher whenever a group of instructions in a branch instruction queue together exhibits a confidence in the accuracy of branch predictions of branch instructions therein that is less than a first predetermined threshold confidence threshold. In one embodiment, the processor includes a fetch throttle controller that inhibits fetch throttling by the instruction fetcher when confidence in the accuracy of a branch prediction for a particular currently issued branch instruction exhibits less than a second predetermined threshold confidence threshold.

Method and apparatus for inhibiting fetch throttling when a processor encounters a low confidence branch instruction in an information handling system

An information handling system includes a processor with an array power management controller. The array power management controller gates off a memory array, such as a cache, to conserve power whenever a group of instructions in a branch instruction queue together as a group exhibits a confidence in the accuracy of branch predictions of branch instructions therein that is less than a first predetermined threshold confidence threshold. In one embodiment of the information handling system, the array power management controller speculatively inhibits the gating off of the memory array when confidence in the accuracy of a branch prediction for a particular currently issued branch instruction exhibits less than a second predetermined threshold confidence threshold. In this manner, the array power management controller again allows access to the memory array in the event a branch redirect is likely.

Method and apparatus for controlling memory array gating when a processor executes a low confidence branch instruction in an information handling system

A method is provided for evaluating two or more instructions in an out of order issue queue during a particular cycle of the queue, to select an instruction for issue during the next following cycle. If an instruction was previously designated to issue during the particular cycle, one or more instructions in the queue are evaluated to determine if any of them are dependent on the designated instruction. For the evaluation, each instruction placed into the queue is accompanied by corresponding logic elements that provide destination to source compares for the instruction. In an embodiment comprising a method, the oldest ready instruction in the queue during a particular cycle is identified. When an instruction was previously designated to issue during the particular cycle, it is determined whether at least a first instruction in the queue complies with each condition in a set of conditions, the set including at least the conditions that the first instruction has a dependency on the designated instruction, and that the first instruction is older than the oldest ready instruction. The first instruction is selected for issue during the next following cycle only if the first instruction complies with each condition in the set.

Method and apparatus for back to back issue of dependent instructions in an out of order issue queue

A method and apparatus for steering instructions dynamically, at issue time, so as to maximize the efficiency of use of execution units being shared by multiple threads being processed by an SMT processor. Resource vectors are used at issue time to redirect instructions, from threads being processed simultaneously, to shared resources for which the multiple threads are competing. The existing resource vectors for instructions that are queued for issuance are analyzed and, where appropriate, dynamically recalculated and modified for maximum efficiency.

Dynamic recalculation of resource vector at issue queue for steering of dependent instructions

A method is disclosed in a data processing system for ensuring processing fairness in simultaneous multi-threading (SMT) microprocessors that concurrently execute multiple threads during each clock cycle. A clock cycle priority is assigned to a first thread and to a second thread during a standard selection state that lasts for an expected number of clock cycles. The clock cycle priority is assigned according to a standard selection definition during the standard selection state by selecting the first thread to be a primary thread and the second thread to be a secondary thread during the standard selection state. If a condition exists that requires overriding the standard selection definition, an override state is executed during which the standard selection definition is overridden by selecting the second thread to be the primary thread and the first thread to be the secondary thread.

An information handling system includes a processor that throttles the instruction fetcher whenever the inaccuracy, or lack of confidence, in branch predictions for branch instructions stored in a branch instruction queue exceeds a predetermined threshold confidence level of inaccuracy or error. In this manner, fetch operations slow down to conserve processor power when it is likely that the processor will mispredict the outcome of branch instructions. Fetch operations return to full speed when it is likely that the processor will correctly predict the outcome of branch instructions.

Method and apparatus for conserving power by throttling instruction fetching when a processor encounters low confidence branches in an information handling system

A method and related apparatus is provided for a processor having a number of registers, wherein instructions are sequentially issued to move through a sequence of execution stages, from an initial stage to a final write back stage. As a method, an embodiment includes the step of issuing a first instruction, such as an FMA instruction, to move through the sequence of execution stages, the first instruction being directed to a specified one of the registers. The method further includes issuing a second instruction to move through the execution stages, the second instruction being issued after the first instruction has issued, but before the first instruction reaches the final write back stage. The second instruction is likewise directed to the specified register, and comprises either a store instruction or a load instruction, selectively. R and W bits corresponding to the specified register are used to ensure that a store instruction does not read data from, and that a load instruction does not write data to the specified register, respectively, before the first instruction is moved to the final write back stage.

Growing community of inventors

Round Rock, TX, United States of America

Raymond Cheung Yeung