From Book Flashcards
(26 cards)
What’s the job of the control unit
Controls flow of data inside CPU
Executed data by following the fetch decode execute cycle
Functions of the ALU
Arithmetic Logic Unit
Does all the calculations
Performs logic operations (AND OR NOT etc)
Contains accumulator register
Function of the cache
Stores regularly used data so CPU can access it quickly- CPU checks for data in Cache first and if it’s not there it moves into RAM
Difference between Von Neumann design and Harvard
Von Neumann uses ONE MEMORY for data and instructions (Harvard used separate memory for each )
What does the program counter (in control unit ) do?
Holds MEMORY ADRESS of the instruction for each cycle
Job of accumulator (in ALU)
Stores intermediate results of calculations in the ALU
Where is the memory address about to be used by the CPU held?
Memory address register (may point to data or a CPU instruction)
Where is the data or instruction about to be used by the CPU held?
Memory data register (this may have been fetched from memory or waiting I be written into memory)
3 stages of fetch in the fetch decode execute cycle
1) copy MEMORY ADDRESS from PROGRAM COUNTER to the MEMORY ADDRESS REGISTER
2) copy instruction stored in MAR address to MEMORY DATA REGISTER
3) Increment (increase) program counter to address if next instruction ready for next cycle
What happens during ‘decode’ of the fetch decode execute cycle ?
Instructions in MDR decoded by CU.
What happens to OS when computer boots up?
Copied from secondary storage to RAM
Name the three tiers of storage and give examples
Primary storage - refers to the memory areas that the CPU can access quickly eg CPU registers, cache, ROM , RAM
Secondary storage- where all data (applications, OS, user files) are stored when not in use. Includes HDDs,SSDs,CDs and SD card
Tertiary storage- used for archives and back ups for massive amounts of data. Eg magnetic tape library
Where is data stored in HDDs
Data stored MAGNETICALLY in small areas called SECTORS within circular tracks (read/write heads on moving arm used to access sectors)
Advantages of HDD over SSD
Cheaper
Higher capacity
Longer read / write life
Advantage of SSD over HDD
Faster
Don’t need defragmenting
More shockproof
Silent
5 main functions of OS
Communicate with internal and external hardware via device drivers
Provide user interface allowing user to interact with computer and vice version
Provide platform for applications to run
Allow computer to multitask by controlling memory resources and CPU
Deal with file management and disk management
Every piece of hardware connected to computer system needs device driver. Whts its purpose
Acts as a ‘translator ‘ for signal between OS and HARDWARE
What’s capacity ?
How much data can be stored in storage device
What is the speed ?
How quickly data can e written (stored ) and read (accessed )
What is durability ?
How the device withstands stress
What is reliability ?
How dependable device is
What is system software ?
Software that enables hardware to operate and / or enables applications to run e.g BIOS, OS, System utilities
Wht does BIOS do?
Controls computer when first switched on
Tests system hardware
Loads OS
What doe OS do?
Set of programs that controls how user interacts with hardware and software of computer system
