CSCI 211 Intro Computer Organization Consists of gates for logic And Or Not Processor Memory I O interface Instructions Instructions are in memory Fetch instruction then execute it Fetch execute cycle More detailed Fetch instruction Fetch operands Execute instruction Save result Determine next instruction Processor Components Datapath Hardware that electrons flow through to accomplish an instruction Control Tells hardware what to do and when to do it Registers Small amount of memory 32 4 byte for MIPS that can be operated upon What s inside Everything in the computer is represented with 0 s and 1 s on off Integers Characters Boolean Float Instructions machine language Languages Machine Language Just 0 s and 1 s Very hard to program Assembly Symbolic for machine language Easy to create a program to translate from assembly language to machine language almost 1 to 1 Keeps track of variables addresses Why Learn Assembler Understand what the machine does Helps you to be a better guesser Needed to write a compiler 431 Needed to build CPUs Faster to execute To determine timing Gives you the power to access anything Maintaining older systems Why not USE assembly Tedious Error prone Slow to write Machine dependent Good compilers produce fast code already MIPS CPU Used in many systems SGI workstations Sony PS2 Dish Network set top box Tivo DVR Pioneer Plasma TV HP Color laser printer Many more MIPS Layout Control Register file 32 registers with 32 bits each ALU Program Counter PC Memory 32 bit address 232 bytes addressable 4Gb Instruction register IR Control Unit Sends the proper control signals to each component to accomplish instruction Input to the control unit Instruction Cycle number which step of the instruction Register File A group of registers Input Which register 5 bits Read or Write 32 bit value for write Outputs a 32 bit value for read Register Conventions 0 0 1 used by the assembler 2 3 function return values 4 7 Arguments to a function Etc Other components ALU Performs arithmetic and logic and or shift PC Program counter address of next instruction Memory 32 bit address Addresses a byte 8 bits Some instructions use word 4 bytes halfword 2 bytes or byte operands All instructions are 4 bytes on MIPS PC PC 4 Instruction Register IR Holds the 32 bit instruction just fetched Needed for control unit to determine what control signals to send Instruction Format Opcode First 6 bits 3 Formats R type Opcode all 0 s Three 5 bit fields for registers 2 for operand 1 for result 5 bit shift amount for shift instructions 6 bit function code Other formats I Type Two 5 bit register numbers 16 bit value as the third operand J type Jump instructions 26 bit address field 64M