👾 The CPU

Question 1

what does CPU stand for?

Answer 1

Central Processing Unit

Question 2

ie. why is it important?

define the purpose of the CPU in a computer

Answer 2

• it is responsible for all of a computer’s processing (like a brain)

Question 3

all connect to the CPU…

What are the main components of a computer (there are 4)?

Answer 3

1. Main memory
2. input devices
3. secondary storage
4. output devices

Question 4

what is the Von Neumann architecture?

Answer 4

A computer architecture model proposed by John von Neumann in the mid-20th century, which forms the basis for most modern computers.

Question 5

what are the components of the Von Neumann architecture (there are 5)?

Answer 5

1. CPU
2. memory unit
3. control unit
4. ALU
5. input/output devices

Question 6

what are the registers in the CPU (there are 4)?

Answer 6

1. program counter
2. ALU
3. Control unit
4. General Purpose Registers

Question 7

explain a program counter

Answer 7

A special purpose register that holds the address of the next instruction to be executed

Question 8

explain the general purpose registers

Answer 8

• they hold data, such as numbers during arithmetic calculations
• Some architectures have just a single register called the Accumulator

Question 9

where is the program counter located?

Answer 9

in the control unit

Question 10

How does the program counter work?

Answer 10

1. The Program Counter points
   to the next instruction that
   needs to be executed
2. The Program Counter is
   incremented after fetching
   an instruction
3. This moves it on to point to
   the next instruction to be
   executed

Question 11

Explain the accumulator

Answer 11

• The accumulator is where
  arithmetic and logic results are
  temporarily stored much like the
  M+ function on a calculator
• Speeds up the storage and retrieval of calculations

Question 12

Why is the accumulator important?

Answer 12

Without the accumulator, it would
be necessary to write the result of
each calculation to main memory (aka. Would take much longer and is a waste of time, so the accumulator does this long, boring job for us instead!)

Question 13

What does ALU stand for?

Answer 13

Arithmetic Logic Unit

Question 14

Explain the ALU (has 3 functions)

Answer 14

It performs:
1. Logical operations
2. Shift operations
3. Arithmetic operations

Question 15

what are the two memory registers to implement the von Neumann architecture?

Answer 15

MAR and MDR

Question 16

what does MAR stand for?

Answer 16

Memory Address Register

Question 17

what are the (3 main) functions of the MAR?

Answer 17

1. Holds the address of the current instruction being done
2. knows the location of data that needs to be accessed
3. keeps track of where data is located

Question 18

what does MDR stand for?

Answer 18

Memory Data Register

Question 19

what are the (2 main) functions of the MDR?

Answer 19

1. Holds the actual data being stored in RAM
2. acts as a buffer and holds data that’s copied from RAM, ready for CPU to process it

Question 20

How does the MDR and the MAR work together?

Answer 20

The MAR knows where to look for data in RAM, and the MDR keeps hold of that data until it’s ready to be used by CPU

Question 21

explain the control unit

Answer 21

it coordinates all the activities taking place

like a comductor of an orchestra

Question 22

what are the main parts of a processor register (6 of them)?

Answer 22

1. accumulator
2. MDR
3. CIR
4. PC
5. MAR
6. Main Memory

Question 23

in a processor register…

what does the PC do?

Answer 23

points to the next instruction

Question 24

in a processor register…

what does CIR stand for?

Answer 24

Current Instruction Register

Question 25

in a processor register…

What is the CIR’s function?

Answer 25

Holds the current instruction to be excecuted

Question 26

how does the CPU operate (hint: it repeats three operations)?

Answer 26

FETCH - DECODE - EXCECUTE

Question 27

FETCH - DECODE - EXECUTE

explain the FETCH operation

Answer 27

causes the next instruction and any data involved to be fetched from the main memory

Question 28

FETCH - DECODE - EXECUTE

explain the DECODE operation

Answer 28

decodes the instruction from FETCH

Question 29

FETCH - DECODE - EXECUTE

explain the EXECUTE operation

Answer 29

carries out the instruction from DECODE

Question 30

what are the three most common factors which affect the CPU’s performance?

Answer 30

1. Clock Speed
2. Processor Cores
3. Type and size of memory

Question 31

explain what clock/ processor speed is

Answer 31

cycles per second measured in hertz (How much instructions is carried out in a second)

1 Kilojerz (KHz) = 1000 cycles

eg. 1 Hertz (Hz) = 1 instruction per sec. 1 kilohertz (KHZ) = 1000 cycle

cycles is the same as instructions

Question 32

How does the amount of processor cores one has affects the performance of the CPU?

Answer 32

Modern CPUs often have multiple processing cores, allowing them to execute multiple tasks simultaneously. More cores generally lead to better multitasking performance and increased throughput. However, sometimes the computer’s don’t utilise these extra cores, and ends up being a waste

Question 33

what is another name for type and size memory?

Answer 33

Cache size/memory

Question 34

define cache memory

Answer 34

• It’s a small amount of very fast, expensive memory in the CPU
• Can be accessed faster than the RAM
• reduces the time required to access frequently used data and instructions, improving overall system performance

Question 35

how does the size of cache memory affect the CPU’s performance?

Answer 35

A larger cache, particularly the level 1 (L1) and level 2 (L2) caches, can reduce the time spent accessing data from main memory

ie. can make the computer run smoother and faster

Question 36

what is the role of cache memory?

Answer 36

serves as a buffer between the CPU and main memory (RAM), storing frequently accessed data and instructions for quick access by the CPU