COSI 131a Lecture Notes - Lecture 2: Processor Register, Instruction Register, Control Flow
14 Sep 2019
School
Department
Course
Professor
Document Summary
The cpu"s control unit consists of a fetch decode execute (fde) unit, a program counter. Memory and i/o (pc) and an instruction register (ir). The operating system is not stored in rom, but instead on disk. The bootstrap loader is a small program stored in rom that runs part of the operating system. Data is transferred from/to memory via 3 cpu registers: memory. Address register (mar), memory data register (mdr), and command register (cmd). There are 2m different addresses we can form with m bits, so we can access 2m words. If each word is 4 bytes (22 bytes), then the total memory we can address is 2m+2 bytes. Main memory is volatile, and the only large storage media that the cpu can access directly. Meanwhile, secondary storage is an extension of main memory that provides large, nonvolatile storage capacity. Programmed i/o consists of i/o instructions that are part of the program, and the cpu executes these instructions.
