CS 25000 Lecture Notes - Lecture 14: Field-Programmable Gate Array, Microcontroller, Microcode
20 Mar 2017
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Document Summary
Evolution of computers: early systems, single cpu controlled entire computer, responsible for all i/o, modern computers, decentralized architecture, cpu chip may contain multiple cores, each i/o decide contains processor, cpu performs computations and coordinates other processors. Imagine different cpus inside a given cpu: mode selects which cpu is currently in use, two modes may have different, number of registers, register size. Instruction sets: changing between modes, automatic change (hardware does its thing) Prior to change, os specified new mode: manual change (under program control) Some modes can be selected by an application. Privilege and protection: number of privilege levels is a design choice: 0 through 8 have been built, levels limit operations allowed so cpu can detect unauthorized operations . Pros: fast update of a processor, errors easy to correct, microcode usually hidden from programmers, cons, execution overhead: macro instructions take multiple clock cycles, microcode usually hidden from programmers; when not hidden, cpu is called reconfigurable .
