1.1.1 architecture of the CPU

Question 1

the purpose of the CPU

Answer 1

the purpoe of a CPU is to process data (central processing unit). it does this using the fetch-execute cycle

Question 2

fetch

Answer 2

the PC hold the address for the instruction
it is copied into the MAR
the MAR carries the address through the address bus (unidirectional) and looks for it in the main memory
the contents of that address are taken to the MDR via he data bus (bidirectional)
the PC increments by one

Question 3

decode

Answer 3

the data from MDR is stored on cache

the data is taken from the MDR or cache and sent to the CU to decode it

Question 4

execute

Answer 4

after the CU figures out what it needs to do with the data, it carries out the instruction
at this point the fetch decode execute cycle is completed

Question 5

FDE

Answer 5

fetch - fetches the instruction from main memory and brings it back to the CPU
decode - inspects the instruction and tries to work out what it needs to be doing
execute - carries out the instruction. this can mean:
going back to main memory to get more data
performing a calculation
soring info back into main memory

this cycle happens billions of times per second which is why our computers get hot

Question 6

what is a compter?

Answer 6

A computer is an electronic device that takes input, processes data and outputs a result. It may also communicate and store processed data.

Question 7

the CPU and its four components

Answer 7

arithmetic logic unit (ALU) - this carries out arithmetic calculations and is responsible for making logical decisions

cache - small, very fast memory. typically located very close to the CPU. stores frequently used instructions and data. its quicker for the CPU to access data from cache than from RAM as its closer t the CPU. cache cannot be increades but RAM can. The CPU first checks if the data that’s required is in cache. If it’s not in cache, then it goes all the way to main memory which will take a bit lopnger

cotrol unit (CU) - sends signals to control data flow around the CPU

registers - small, temporary very fast memory with a specific purpose. located inside the CPU

Question 8

Registers

Answer 8

accumulator - holds the results of calsulaions

memory address register (MAR) - holds the address of where data needs to be fetched from

memory data register (MDR) - holds data fetched from or to be writeen to main memory

program counter (PC) - holds the address of he ext instruction (incraments by one)

Question 9

von neumann architecture

Answer 9

key characterisics:
central processing unit (CPU)
cache
inputs and outputs
interna clock

this architecture compter fetches, decodes and exectes instructions

von neumann allows data and programs to be stored in the same memory space in a binary format