Advanced Micro Devices Corporation

Freescale Semiconductor,inc.

Texas Instruments Corporation

Andes Technology Corporation

Synopsys, Inc.

Other

Analog Devices,inc.

Nxp Usa, Inc.

Advanced Micro Design, Inc.

Thang M Tran

David B Witt

Rupaka Mahalingaiah

Rammohan Narayan

William M Johnson

James K Pickett

Andrew McBride

Muralidharan Santharaman Chinnakonda

Shane A Southard

Karthikeyan Muthusamy

Wade A Walker

Ravi P Singh

Derrick R Meyer

Michael Brian Schinzler

Edmund Joseph Gieske

Mauricio Calle

Trinh Huy Nguyen

Deepa Duraiswamy

Srikanth Kannan

Trinh Huy H Nguyen

John G Bartkowiak

Michael D Goddard

Marty Lynn Pflum

Jeffrey L Nye

Paul K Miller

Teik-Chung Tan

David Edward Kroesche

Roman Staszewski

Rajinder Paul Singh

Murali S Chinnakonda

Gopi Ganapathy

Stephen Charles Kromer

Hebbalalu S Ramagopal

Leick D Robinson

Sam Brandon Sandbote

Robert C Thaden

H S Ramagopal

Raul A Garibay, Jr

Mike Pedneau

James Yang

Matt T Gavin

Jagadish V Nayak

Jinwen Xi

A microprocessor and a method for issuing a load/store instruction is introduced. The microprocessor includes a decode/issue unit, a load/store queue, a scoreboard, and a load/store unit. The scoreboard includes a plurality of scoreboard entries, in which each scoreboard entry includes an unknown bit value and a count value, wherein the unknown bit value or the count value is set when instructions are issued. The decode/issue unit checks for WAR, WAW, and RAW data dependencies from the scoreboard and dispatches load/store instructions to the load/store queue with the recorded scoreboard values. The load/store queue is configured to resolve the data dependencies and dispatch the load/store instructions to the load/store unit for execution.

Microprocessor and method for speculatively issuing load/store instruction with non-deterministic access time using scoreboard

A microprocessor that includes a shared functional unit, a first execution queue and a second execution queue is introduced. The first execution queue includes a plurality of entries, wherein each entry of the first execution queue includes a first count value which is decremented until the first count value reaches 0. The first execution queue dispatches the first-type instruction to the shared functional unit when the first count value reaches 0. The second execution queue include a plurality of entries, wherein each entry of the second execution queue comprises a second count value which is decremented until the second count value reaches 0. The second execution queue dispatches the second-type instruction to the shared functional unit when the second count value reaches 0. The issue unit resolves all data dependencies and resource conflicts so that the first and second count values are preset for the first-type and second-type instructions to be mutually executed at the exact time in the future by the shared functional unit.

Microprocessor with shared functional unit for executing multi-type instructions

A processor that includes a register file, a read shifter, a decode unit and a plurality of functional units is introduced. The register file includes a read port. The read shifter includes a plurality of shifter entries and is configured to shift out a shifter entry among the plurality of shifter entries every clock cycle. Each of the plurality of shifter entries is associated with a clock cycle and each of the plurality of shifter entries comprises a read value that indicates an availability of the read port of the register file for a read operation in the clock cycle. The decode unit is coupled to the read shifter and is configured to decode and issue an instruction based on the read values included in the plurality of shifter entries of the read shifter. The plurality of functional units is coupled to the decode unit and the register file and is configured to execute the instruction issued by the decode unit and perform the read operation to the read port of the register file.

Processor having read shifter and controlling method using the same

A microprocessor using a counter in a scoreboard is introduced to handle data dependency. The microprocessor includes a register file having a plurality of registers mapped to entries of the scoreboard. Each entry of the scoreboard has a counter that tracks the data dependency of each of the registers. The counter decrements for every clock cycle until the counter resets itself when it counts down to 0. With the implementation of the counter in the scoreboard, the instruction pipeline may be managed according to the number of clock cycles of a previous issued instruction takes to access the register which is recorded in the counter of the scoreboard.

Microprocessor having self-resetting register scoreboard

A microprocessor includes a translation look-aside buffer (TLB) having a plurality of TLB entries addressable by a branch address and having a branch target buffer (BTB), including a plurality of BTB entries addressable by the branch address. Each TLB entry includes a virtual address. Each BTB entry including a branch tag-way data and a target tag-way data. To perform a branch prediction, the BTB and TLB are accessed, where the TLB way associative data representing one of N sets of TLB entries is used to determine BTB hit or BTB miss. If BTB hit, the branch target address of the branch address may be obtained by accessing the TLB using target tag-way data in the BTB, or by using the branch page address when a same page bit in the hit BTB entry is set.

Apparatus and method for using instruction translation look-aside buffers in the branch target buffer

In the disclosure, the microprocessor resolves the conflicts in decode stage and schedules the instruction to be executed at a future time. The instruction is issued to an execution queue until the scheduled time in the future when it is dispatched to a functional unit for execution. The disclosure uses a counter for the functional unit to track when the resource is available in the future to accept the next instruction. The disclosure also tracks the future N cycles when the register file read and write ports are scheduled to read and write operand data.

Microprocessor with pipeline control for executing of instruction at a preset future time

A processor that includes a register file, a latency shifter, a decode unit and a plurality of functional units is introduced. The register file includes a write port. The latency shifter includes a plurality of shifter entries and shifts out a shifter entry among the shifter entries every clock cycle. Each of the shifter entries is associated with a clock cycle and each of shifter entries includes a writeback value that indicates whether the write port of the register file is available for a writeback operation in the associated clock cycles. The decode unit is configured to decode an instruction and issue the instruction according to the writeback value of the latency shifter. The functional units are coupled to the decode unit and the register file and are configured to execute the instruction issued by the decode unit and perform writeback operation to the write port of the register file.

Processor having latency shifter and controlling method using the same

Embodiments of the present disclosure support implementation of a Level-1 (L1) cache in a microprocessor based on independently accessed data and tag arrays. Presented implementations of L1 cache do not require any stall pipeline mechanism for stalling execution of instructions, leading to improved microprocessor performance. A data array in the cache is interfaced with one or more data index queues that comprise, upon occurrence of a conflict between at least one instruction requesting access to the data array and at least one other instruction that accessed the data array, at least one data index for accessing the data array associated with the at least one instruction. A tag array in the cache is interfaced with a tag queue that stores one or more tag entries associated with one or more data outputs read from the data array based on accessing the data array.

Modulization of cache structure utilizing independent tag array and data array in microprocessor

An execution pipeline architecture of a microprocessor employs a third-pass functional unit, for example, third-level of arithmetic logic unit (ALU) or third short-latency execution unit to execute instructions with reduced complexity and area cost of out-of-order execution. The third-pass functional unit allows instructions with long latency execution to be moved into a retire queue. The retire queue further includes the third functional unit (e.g., ALU), a reservation station and a graduate buffer. Data dependencies of dependent instructions in the retire queue is handled independently from the main pipeline.

Triple-pass execution using a retire queue having a functional unit to independently execute long latency instructions and dependent instructions

Embodiments of the present disclosure support hardware based thread switching in a multithreading environment. The thread switching is implemented on a multithread microprocessor by utilizing thread mailbox registers and other auxiliary registers that can be pre-programmed for hardware based thread switching. A set of mailbox registers can be allocated to each thread of a plurality of threads that can be executed in the microprocessor. A mailbox register in the set of mailbox registers comprises an identifier of a next thread of the plurality of threads to which an active thread switches based on a thread switch condition further indicated in the mailbox register. The auxiliary registers in the microprocessor can be used to configure a number of threads for simultaneous execution in the microprocessor, a priority for thread switching, and to store a program counter of each thread and states of registers of each thread.

Communication between threads of multi-thread processor

Various embodiments of a microprocessor include a scoreboard implementation that directs the microprocessor to the location of data values. For example, the scoreboard may include individual bits that instruct the microprocessor to retrieve the data from a re-order buffer, retire queue, result bus, or register file. As a first step, the microprocessor receives an instruction indicating a process that requires data from one or more source registers. Instead of automatically retrieving the data from the register file, which is a costly process, the microprocessor may read the scoreboard to determine whether the needed data can be more cost-effectively retrieved from the re-order buffer, retire queue, or result busses. Therefore, the microprocessor can avoid costly data retrieval procedures. Additionally, the scoreboard implementation enables the microprocessor to handle limited out-of-order instructions, which improves overall performance of the microprocessor.

Reorder buffer scoreboard having multiple valid bits to indicate a location of data

Certain embodiments of the present disclosure support a method and apparatus for efficient multithreading on a single core microprocessor. Thread switching in the single core microprocessor presented herein is based on a reserved space in a memory allocated to each thread for storing and restoring of registers in a register file. The thread switching is achieved without full save and restore of the register file, and only those registers referenced in the memory are saved and restored during thread switching.

Thread switching in microprocessor without full save and restore of register file

A processor may efficiently implement register renaming and checkpoint repair even in instruction set architectures with large numbers of wide (bit-width) registers by (i) renaming all destination operand register targets, (ii) implementing free list and architectural-to-physical mapping table as a combined array storage with unitary (or common) read, write and checkpoint pointer indexing and (iiii) storing checkpoints as snapshots of the mapping table, rather than of actual register contents. In this way, uniformity (and timing simplicity) of the decode pipeline may be accentuated and architectural-to-physical mappings (or allocable mappings) may be efficiently shuttled between free-list, reorder buffer and mapping table stores in correspondence with instruction dispatch and completion as well as checkpoint creation, retirement and restoration.

Space efficient checkpoint facility and technique for processor with integrally indexed register mapping and free-list arrays

A mechanism to generate a self-clock within a synchronous processing unit of an asynchronous digital device. The self-clock is designed to match the worst-case delay of pipeline processing unit in such a way that the pipeline processing unit is operate at its own natural clock frequency and shutting off when there is no valid data to process. The synchronization logic of the processing unit consists of self-clock that generates output clock to synchronize with the internal clock edge if the processing unit is active or synchronize with the input clock edge if the processing unit is inactive.

Method and apparatus for processor to operate at its natural clock frequency in the system

A microprocessor system is disclosed that includes a first data cache that is shared by a first group of one or more program threads in a multi-thread mode and used by one program thread in a single-thread mode. A second data cache is shared by a second group of one or more program threads in the multi-thread mode and is used as a victim cache for the first data cache in the single-thread mode.

Systems and methods for reconfiguring cache memory

Growing community of inventors

Austin, TX, United States of America

Thang M Tran