1.1 structure and function of the CPU

Question 1

what is the ALU and what is its job?

Answer 1

the arithmetic logic unit, this carries out calculations and logical decisions.

Question 2

what is the control unit and what is its job?

Answer 2

The control unit sends out signals to co-ordinate the processor. Controls how the data moves around parts of the CPU and how it moves between CPU and memory.

Question 3

what are buses?

Answer 3

buses are a pathway for electrical signals to travel on.

Question 4

what is a register?

Answer 4

a register is a memory location inside the processor that can hold one instruction.

Question 5

what kind of registers are there?

Answer 5

• program counter
• accumulator
• memory data register
• memory address register
• current instruction register.

Question 6

what is a program counter?

Answer 6

a program counter is a register that keeps track of the line of code being executed. It gets incremented to point to the next instruction, with each cycle of the FDE cycle, allowing the program to be ran line by line.

Question 7

what is an accumulator?

Answer 7

an accumulator is a register that

stores the results of the calculations made by the ALU.

Question 8

what is a MDR?

Answer 8

MDR is a memory data register and it stores the data that has been fetched from or stored in memory.

Question 9

what is a MAR?

Answer 9

MAR is a memory address register and it stores the address of the data or instructions that are to be fetched or sent.

Question 10

what is a CIR?

Answer 10

CIR is a current instruction register and it stores the most recently fetched instruction waiting to be decoded and executed.

Question 11

what is machine code?

Answer 11

Machine code is binary instruction and is split into OPCODE and data it is very effective as it means the computer has to do less work to carry out the instruction but not user friendly.

Question 12

what is assembly code?

Answer 12

Assembly code is one above machine code and allows the programmer to read/write code easier. The mnemonic for the op code is three letters.

Question 13

what are high level languages?

Answer 13

High level languages like python is easiest for coding as it is easy to understand and read.

Question 14

what is the FDE cycle/

Answer 14

FDE- fetch, decode, execute.

Question 15

what is a clock cycle?

Answer 15

A single clock cycle is a complete FDE cycle.

Question 16

what is clock speed measured in?

Answer 16

Clock speed is measured in hertz.

Question 17

what is the advantage of having a faster clock speed?

Answer 17

The greater clock speed the more calculations can be carried out per second.

Question 18

what is cache?

Answer 18

Cache memory is a special type of fast memory used for instructions and data likely to be needed by the processor.

Question 19

what are the three levels of cache memory?

Answer 19

Three levels of cache memory are L1, L2 and L3.

L1 being the smallest and L3 being the biggest but furthest away from processor.

L3 is a shared cache between multiple cores.

Question 20

what are the limitations of cache?

Answer 20

• it is very expensive.
• Must be physically small to fit onto the chip.
• Performance decreases as memory size increases.

Question 21

why do processors usually have more than one core?

Answer 21

it becomes increasingly harder to improve clock speed so manufacturers increase the number of cores on a chip, more cores means the more data processed at the same time.

Question 22

what is the disadvantage of multi core processors?

Answer 22

having more than one core, for example quad core, this does not mean the data is processed four times as fast as not all processes can be split down into multiple cores.

Question 23

what is the John Von Neuman architecture?

Answer 23

In the john von Neumann architecture the programs and data is held in the memory; the processor and memory are separate and the data moves between the two.

Question 24

what is the Von Neuman bottleneck?

Answer 24

The bottle neck is caused by the processor being so fast that it processes data faster than the memory can transfer it so the CPU is left idle longer the faster it is.

Question 25

what is the Harvard architecture and how does it get rid of the bottle neck?

Answer 25

The Harvard architecture has two separate buses to the data and memory, this gets rid of the bottle neck as having two separate buses to instructions and the data memory gets rid of the delay of having the CPU idle waiting for the data.

Question 26

what is a microprocessor?

Answer 26

A dedicated processor for carrying a specific, narrow or constrained task.

Question 27

what is a SoC?

Answer 27

A SoC (system on chip) is a integrated circuit that has all components of a computer or other electronic system on a single chip.

Question 28

what is pipelining?

Answer 28

loading the next instruction while the last one is being processed. it only works if the next instruction can be predicted.