Imagination Technologies Limited

Mips Tech Limited

Andrew David Webber

Robert Graham Isherwood

Ian Oliver

Daniel Ángel Chaver Martínez

Enrique Sedano Algarabel

A method and an apparatus are provided for selecting between a plurality of instruction sets available to a microprocessor. An instruction fetch address is supplied. At least one predetermined bit of the instruction fetch address is used to select between the instruction sets. Once an instruction set has been selected, instructions may be fetched and decoded with a decoding scheme appropriate to the instruction set.

Method and apparatus for selecting among a plurality of instruction sets to a microprocessor

A method in an instruction fetch unit configured to initiate a fetch of an instruction bundle from a first memory and to initiate a fetch of an instruction bundle from a second memory, wherein a fetch from the second memory takes a predetermined fixed plurality of processor cycles, the method comprising: identifying that an instruction bundle is to be selected for fetching from the second memory in a predetermined future processor cycle; and initiating a fetch of the identified instruction bundle from the second memory a number of processor cycles prior to the predetermined future processor cycle based upon the predetermined fixed plurality of processor cycles taken to fetch from the second memory.

Fetching instructions in an instruction fetch unit

A method to dynamically determine which instructions from a plurality of available instructions to issue in each clock cycle in a multithreaded processor capable of issuing a plurality of instructions in each clock cycle, comprises the steps of: determining a highest priority instruction from the plurality of available instructions; determining the compatibility of the highest priority instruction with each of the remaining available instructions; and issuing the highest priority instruction together with other instructions compatible with the highest priority instruction in the same clock cycle; wherein the highest priority instruction cannot be a speculative instruction. The effect of this is that speculative instructions are only ever issued together with at least one non-speculative instruction.

Method and apparatus for scheduling the issue of instructions in a multithreaded processor

A method and apparatus are provided for executing instructions of a multi-threaded processor having multiple hardware threads with differing hardware resources comprising the steps of receiving a plurality of streams of instructions and determining which hardware threads are able to receive instructions for execution, determining whether a thread determined to be available for executing an instructions has the hardware resources available required by that instructions and executing the instruction in dependence on the result of the determination.

Scheduling execution of instructions on a processor having multiple hardware threads with different execution resources

A method and a system are provided for prioritising the fetching of instructions for each of a plurality of executing instruction threads in a multi-threaded processor. Instructions come from at least one source of instructions. Each thread has a number of threads buffered for execution in an instruction buffer. A first metric for each thread is determined based on the number of instructions currently buffered. A second metric is then determined for each thread, this being an execution based metric. A priority order for the threads is determined from the first and second metrics, and an instruction is fetched from the source for the thread with the highest determined priority which is requesting an instruction.

Prioritising of instruction fetching in microprocessor systems

The invention is a method and system for providing trace data in a pipelined data processor. Aspects of the invention include providing a trace pipeline in parallel to the execution pipeline, providing trace information on whether conditional instructions complete or not, providing trace information on the interrupt status of the processor, replacing instructions in the processor with functionally equivalent instructions that also produce trace information and modifying the scheduling of instructions in the processor based on the occupancy of a trace output buffer.

System for providing trace data in a data processor having a pipelined architecture

A method and apparatus are provided for executing instructions of a multi-threaded processor having multiple hardware threads () with differing hardware resources comprising the steps of receiving a plurality of streams of instructions () and determining which hardware threads are able to receive instructions for execution (), determining whether a thread determined to be available for executing an instructions has the hardware resources available required by that instructions () and executing the instruction in dependence on the result of the determination ().

A method and a system are provided for prioritizing the fetching of instructions for each of a plurality of executing instruction threads in a multi-threaded processor. Instructions come from at least one source of instructions. Each thread has a number of threads buffered for execution in an instruction buffer. A first metric for each thread is determined based on the number of instructions currently buffered. A second metric is then determined for each thread, this being an execution based metric. A priority order for the threads is determined from the first and second metrics, and an instruction is fetched from the source for the thread with the highest determined priority which is requesting an instruction.

A method is provided for dynamically determining which instructions from a plurality of available instructions to issue in each clock cycle in a multithreaded processor capable of issuing a plurality of instructions in each clock cycle. The method includes the steps of: determining a highest priority instruction from the plurality of available instructions; determining the compatibility of the highest priority instruction with each of the remaining available instructions; and issuing the highest priority instruction together with other instructions compatible with the highest priority instruction in the same clock cycle. The highest priority instruction cannot be a speculative instruction. The effect of this method is that speculative instructions are only ever issued together with at least one non-speculative instruction.

Method and apparatus for scheduling the issue of instructions in a multithreaded microprocessor

The invention is a method and system for providing trace data in a pipelined data processor. Aspects of the invention including providing a trace pipeline in parallel to the execution pipeline, providing trace information on whether conditional instructions are complete or not, providing trace information on the interrupt status of the processor, replacing instructions in the processor with functionally equivalent instructions that also produce trace information and modifying the scheduling of instructions in the processor based on the occupancy of the trace output buffer.

A method and apparatus are provided for executing instructions from a plurality of instruction threads on a multi-threaded processor. The instruction threads may each include instructions of different complexity. A plurality of pipelines for executing instructions are provided and an instruction scheduler determines on each clock cycle the pipelines upon which instructions will be executed. Some of the pipelines are configured to appear to the instruction threads as single pipelines but in fact include two pipeline paths, one for executed instructions of lower complexity and the other. The instruction scheduler determines on which of the two pipeline paths an instruction should execute.

Multithreaded processor with fast and slow paths pipeline issuing instructions of differing complexity of different instruction set and avoiding collision

An apparatus for executing fixed width instructions in a multiple execution unit system has a device for fetching instructions from a memory, and a decoder for decoding each fetched instruction in turn. A determination is made as to whether each decoded instruction includes a portion to fetch a locally stored instruction from a local store. If it does, the locally stored instruction is fetched and locally stored portion are executed.

Expanded functionality of processor operations within a fixed width instruction encoding

A method and apparatus are provided for controlling instructions provided by a microprocessor output port to other execution units. A microprocessor pipeline of instructions is provided for each execution unit. These are scheduled via the microprocessor unit for each execution unit, a determination is made as to whether or not the execution unit can receive further instructions. If it cannot, it's associated pipeline is said to be stalled and instructions are deleted from the microprocessor pipeline. Its thread can then be restarted at a later time with the instruction corresponding to the instruction which was unable to execute.

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Tring, United Kingdom

Andrew David Webber