Advanced Micro Devices Corporation

Brian W Case

Rod G Fleck

Cheng-Gang Kong

William M Johnson

Ole H Moller

Philip M Freidin

Gigy Baror

Timothy A Olson

Smeeta Gupta

David I Sorensen

Ole Moller

A streamlined instruction processor processes data in response to a program composed of prespecified instructions in pipeline cycles. The processor comprises an instruction fetch unit, including an instruction interface adapted for connection to an instruction memory and for fetching instructions from the instruction memory. The instruction fetch unit includes an instruction prefetch buffer coupled to the instruction interface for buffering a sequence of instructions supplied to the instruction interface. A branch target cache is coupled with the prefetch buffer for storing sets of instructions retrieved from a corresponding set of locations in the instruction memory, having sequential instruction addresses. The first instruction in each such set is a branch target instruction in the program. In addition, an execution unit including a data interface adapted for connection to the data memory, executes the instructions in pipeline cycles. The execution unit includes a storage facility, coupled to the data interface, for storing data in a file of data locations identified by file addresses. The storage facility includes at least two read ports and one write port operable in response to file addresses. An addressing unit coupled to receive the instructions from the instruction register, supplies the file addresses to the read ports and the write port under program control. In addition, the addressing unit is operable in response to a stack pointer providing dynamic allocation of the file of data locations to processes within the program. A memory management unit is coupled to the data interface. The memory management unit includes an address interface adapted for connection to the data memory and the instruction memory for supplying instruction addresses to the instruction memory and data addresses to the data memory, in a simple single access mode, a pipeline mode and a burst mode.

Streamlined instruction processor

A high speed register file for use by an instruction processor suitable for reduced instruction-set computers (RISCs) is disclosed which is preferably used with an efficient register allocation method. The register file facilitates the passing of parameters between procedures by dynamically providing overlapping registers which are accessible to both procedures. Each procedure also has a set of 'local' registers assigned to it which are inaccessible from other procedures. The register file is divided into a number of blocks and a protection register stores a word which proscribes access by a particular procedure or task to certain blocks. In this manner, an instruction processor using the register file can operate on multiple tasks maintaining the integrity of each from undesired changes occuring in the others.

General-purpose register file optimized for intraprocedural register

An instruction processor suitable for use in a reduced instruction-set computer employs an instruction pipeline which performs conditional branching in a single processor cycle. The processor treats a branch condition as a normal instruction operand rather than a special case within a separate condition code register. The condition bit and the branch target address determine which instruction is to be fetched, the branch not taking effect until the next-following instruction is executed. In this manner, no replacement of the instruction which physically follows the branch instruction in the pipeline need be made, and the branch occurs within the single cycle of the pipeline allocated to it. A simple circuit implements this delayed-branch method. A computer incorporating the processor readily executes special-handling techniques for calls on subroutine, interrupts and traps.

System for processing single-cycle branch instruction in a pipeline

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Sunnyvale, CA, United States of America

Brian W Case