3.1 computer architecture Flashcards
what is the role of the CPU
processes instructions and data input into computer so result can be output
what is a microprocessor
- integrated circuit contained on single chip
- accepts data into computer & processes into information ready for output
what are the components in a CPU
- units: ALU, CU
- registers: PC, MAR, MDR, CIR, ACC
- buses: address bus, data bus, control bus
purpose of CU
- control operation of memory
- sends control signals that manage transfer of data and instructions within CPU
- initiates each step of FDE cycle
purpose of ALU
- perform arithmetic calculations or logical operations
- use ACC to temp store data
purpose of PC
- stores address of next instruction
- to be fetched from memory
purpose of MAR
- store address of instruction
- to retrieve data from specific memory location
purpose of MDR
- store data from address in MDR
- send data to CIR
purpose of CIR
- store instruction
- which CPU currently decoding/executing
purpose of ACC
- hold temporary values from calculations
- worked on by ALU
what are registers
- small areas of storage in CPU
- extremely fast to access
purpose of control bus
- carries control signals from CU to other components
- carries read/write signals from CPU to RAM
purpose of data bus
- bidirectional
- write operation: carry data to be written MDR –> RAM
- read operation: carry data RAM –> MDR
purpose of address bus
- unidirectional
- carry addresses MAR –> RAM
- indicate which address will be selected
what is broad process of FDE cycle
fetch: instruction fetched from RAM –> CPU
decode: instruction decoded by CU to determine what type of instruction it is
execute: instruction executed, usually by ALU
describe fetch processes in FDE cycle
- PC contain address of next instruction
- contents of PC copied to MAR
- PC incremented by 1
- address bus carries value in MAR –> RAM
- control bus send read signal to RAM
- data bus carries contents of desired RAM address to MDR
- contents of MDR copied to CIR
describe decode processes in FDE cycle
instruction in CIR decoded by CU
describe execute processes in FDE cycle
- instruction sent to ALU to be executed
- ALU may use ACC to temporarily store results
what is stored program concept
- instruction stored in main memory
- instructions fetched, decoded, executed by processor
- programs can be moved to and from main memory
what is memory concpet
- computer’s memory is divided into partitions
- each partition consists of an address and its contents
what is an instruction set
- list of all commands that CPU can process
- commands are in machine code
what is core in CPU
- processor within CPU to carry out FDE cycle
- single core can work on 1 instruction at a time
how does number of cores in CPU affect performance
- multi-core CPU can work on more instructions simultaneously
- helpful for running several tasks at once
- BUT individual programs often have instructions must run in sequence, so do not benefit significantly
what is cache in CPU
extremely high speed memory in CPU, store temporary copies of most commonly accessed RAM locations
how does cache affect CPU performance
faster fetch process.
what is clock in CPU
determines number of cycles CPU can perform in a second (measured in GHz)
how does clock speed affect CPU performance
- higher clock speed means quicker FDE cycle
- also use more energy, produce more heat
what is embedded system
- computer system
- performs dedicated, single function inside another appliance
what are characteristics of embedded systems
- rugged operating systems
- low power consumption
- limited processing resources (more difficult to program, interact)
- small size
- low cost per unit
process of embedded system
- input from user sent to microprocessor (ADC if data analogue)
- data from user interface also sent to microprocessor
- microprocessor send signals to actuators, output
what is a bus CPU
way of communicating between components
what are the factors affecting performance of CPU
- clock speed
- size of cache
- core
how does cache work
- store frequently used instructions/data that need to be accessed faster
- when CPU tries to read data from address, first check if location exists in cache
cache hit: access data from faster cache
cache miss: access from slower RAM
what is cache
- cache memory located within CPU
- allow faster access to CPU
how is embedded system different from general purpose computer
- general purpose can perofrm many diff functions
advantages of embedded sytems
- compact
- easy for mass production
- less expensive
- highly reliable/efficient
disadvantages of embedded systems
- hard for maintenance
- difficult to reprogram/repurpose
- designed to be disposable
- hard to take backup of embedded files
