Cycles Per Instruction
In computer architecture, cycles per instruction (aka clock cycles per instruction, clocks per instruction, or CPI) is one aspect of a processor's performance: the average number of clock cycles per instruction for a program or program fragment. It is the multiplicative inverse of instructions per cycle. Definition The average of Cycles Per Instruction in a given process is defined by the following: CPI = \frac Where IC_i is the number of instructions for a given instruction type i, CC_i is the clock-cycles for that instruction type and IC=\Sigma_i(IC_i) is the total instruction count. The summation sums over all instruction types for a given benchmarking process. Explanation Let us assume a classic RISC pipeline, with the following five stages: # Instruction fetch cycle (IF). # Instruction decode/Register fetch cycle (ID). # Execution/Effective address cycle (EX). # Memory access (MEM). # Write-back cycle (WB). Each stage requires one clock cycle and an instruction passes ...
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Computer Architecture
In computer engineering, computer architecture is a description of the structure of a computer system made from component parts. It can sometimes be a high-level description that ignores details of the implementation. At a more detailed level, the description may include the instruction set architecture design, microarchitecture design, logic design, and implementation. History The first documented computer architecture was in the correspondence between Charles Babbage and Ada Lovelace, describing the analytical engine. When building the computer Z1 in 1936, Konrad Zuse described in two patent applications for his future projects that machine instructions could be stored in the same storage used for data, i.e., the stored-program concept. Two other early and important examples are: * John von Neumann's 1945 paper, First Draft of a Report on the EDVAC, which described an organization of logical elements; and *Alan Turing's more detailed ''Proposed Electronic Calculator'' ...
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