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In computer engineering, instruction pipelining is a technique for implementing instruction-level parallelism within a single processor. Pipelining attempts to keep every part of the processor busy with some instruction by dividing incoming instructions into a series of sequential steps (the eponymous "pipeline") performed by different processor units with different parts of instructions ...
The first machine to use out-of-order execution was the CDC 6600 (1964), designed by James E. Thornton, which uses a scoreboard to avoid conflicts. It permits an instruction to execute if its source operand (read) registers aren't to be written to by any unexecuted earlier instruction (true dependency) and the destination (write) register not be a register used by any unexecuted earlier ...
This category contains articles related to instruction processing by microprocessors. Subcategories This category has the following 6 subcategories, out of 6 total.
Instruction-level parallelism (ILP) is the parallel or simultaneous execution of a sequence of instructions in a computer program. More specifically, ILP refers to the average number of instructions run per step of this parallel execution.
The main common concept of each design is a five-stage execution instruction pipeline. During operation, each pipeline stage works on one instruction at a time. Each of these stages consists of a set of flip-flops to hold state, and combinational logic that operates on the outputs of those flip-flops.
The pipelined architecture allows multiple instructions to overlap in execution, much like an assembly line. The pipeline includes several different stages which are fundamental in microarchitecture designs. [5] Some of these stages include instruction fetch, instruction decode, execute, and write back.
C = A+B needs four instructions. 3-operand, allowing better reuse of data: [11] CISC — It becomes either a single instruction: add a,b,c. C = A+B needs one instruction. CISC — Or, on machines limited to two memory operands per instruction, move a,reg1; add reg1,b,c; C = A+B needs two instructions.
Very long instruction word (VLIW) refers to instruction set architectures that are designed to exploit instruction-level parallelism (ILP). A VLIW processor allows programs to explicitly specify instructions to execute in parallel, whereas conventional central processing units (CPUs) mostly allow programs to specify instructions to execute in sequence only.