3.1 Computer Structure

Question 1

What is the role of the CPU in a computer?

Answer 1

The CPU processes instructions and data that are input into the computer so the result can be output.

Question 2

What is a microprocessor?

Answer 2

A microprocessor is a type of integrated circuit on a single chip.

Question 3

What are the components of a CPU in a Von Neumann architecture?

Answer 3

UNITS:
- Arithmetic & Logic Unit (ALU)
- Control Unit (CU), including system clock

REGISTERS:
- program counter (PC)
– memory address register (MAR)
– memory data register (MDR) // memory buffer register (MBR)
– current instruction register (CIR)
– accumulator (ACC)

BUSES:
– address bus
– data bus
– control bus

Question 4

What are the components other than the CPU in the Von Neumann Model?

Answer 4

• Immediate Access Store (IAS)
• Main Memory (RAM)
• Input Device
• Output Device
• Secondary Storage Device

Question 5

What is the function(s) of the Immediate Access Store(IAS)?

Answer 5

It temporarily holds data and instructions waiting to be processed after they are loaded from the main memory.

Question 6

Another name for IAS(Immediate Access store)?

Answer 6

The Immediate Access Store (IAS) is another name for primary main memory (RAM).

Question 6

Why is IAS(immediate access store) used?

Answer 6

It is used because read or write operations carried out using the IAS are considerably faster, and so any key data needed by an application will be stored temporarily in the IAS to speed up operations.

Question 7

What is the main memory, and how is it used in the Von Neumann model for a computer system?

Answer 7

• Main memory refers to primary memory, or RAM.
• It is a volatile memory.
• It is used to hold data or instructions that are currently in use.
• It is directly accessed by the central processing unit (CPU).

Question 8

What is the ‘Stored program concept’ when applied to the Von Neumann Model?

Answer 8

• The program is stored on a secondary storage device.
• The data and instructions are moved to main memory (RAM).
• The data and instructions are stored in the same memory or RAM.
• The data and instructions are moved to registers to be executed.
• The instructions are fetched and executed in a sequence, one after another.

Question 9

WHAT IS THE PURPOSE BEHIND INPUT/OUTPUT DEVICES?

Answer 9

• It is used to allow interaction with the computer.
• Input device allows data to be entered into a computer system (e.g., keyboard, touch screen
  & microphone, etc.).
• Output device allows the user to view/hear the data that has been entered into a computer system (e.g., printer, monitor & loudspeaker, etc.).

Question 10

WHAT ARE THE MAIN COMPONENTS OF A CPU?

Answer 10

• arithmetic logic unit (ALU)
• the control unit(CU)
• the system clock.

Question 11

What are the function(s) of an Arithmetic logic unit(ALU)?

Answer 11

• It is the component WITHIN the CPU that carries out calculations.
• It performs arithmetic operations such as addition, subtraction, multiplication, division, and logical operations or comparisons such as AND, OR, NOT, etc.
• It holds temporary values during calculations in a register called the accumulator (ACC).

Question 12

What are the function(s) of a control unit(CU)?

Answer 12

• It is the component WITHIN the CPU that controls the flow of data and manages operations between the components of the CPU (processor).
• It sends or receives control signals that manage the transfer of data and execution of instructions within the CPU.
• It decodes an instruction using an instruction set.

Question 13

What is a register?

Answer 13

• A register is a small piece of fast memory.
• It is a temporary storage of data and instructions that is about to be or has been processed.
• It is part of the processor.
• A register can be general or special-purpose.

Question 14

What are the function(s) of a Memory Address Register(MAR)?

Answer 14

• It holds the address of the next or current instruction to be fetched or processed.
• It holds the memory address of where the data needs to be stored.
• It uses the address bus to send an address to another component.

Question 15

What is the function of the Memory Data/Buffer register(MDR)?

Answer 15

• It holds data or instructions that are in use and has been fetched from the memory/the address stored in MAR.
• It is a temporary storage of data between the CPU and primary memory.

Question 16

What are the function(s) of a Program Counter(PC)?

Answer 16

• It holds the address of the next or current instruction to be fetched or processed, or executed.
• It uses the address bus to send an address to another component.
• It increments to point to the address of the next instruction to be fetched and so stores the
  number of processes that have been completed.

Question 17

What are the function(s) of the Current Instruction Register(CIR)?

Answer 17

• It holds the data received from the MDR.
• It holds the current instruction that is to be executed/being processed.

Question 18

What are the function(s) of an Accumulator(ACC)?

Answer 18

• It is built into the arithmetic logic unit (ALU).
• It temporarily holds the result of a calculation OR temporarily holds the data that is currently being used in a calculation.

Question 19

What are the function(s) of memory?

Answer 19

• The computer memory is made up of a number of partitions; each consisting of an address and its contents.
• The address uniquely identifies each location in the memory and the content is the binary
  value stored in each location.

Question 20

What is the purpose of buses?

Answer 20

They are used to connect together the internal components of the CPU and provide a pathway for transmitting data and instructions.

Question 21

PROPERTIES OF ADDRESS BUS

Answer 21

• It is a unidirectional bus (signals travel in one direction only).
• It carries signals relating to addresses between the CPU/processor and the memory of the
  next item to be fetched.

Question 22

PROPERTIES OF WIDTH OF THE ADDRESS BUS

Answer 22

• The width of the address bus determines the number of directly accessible memory locations.
• Increasing the width of the address bus significantly increases the number of directly accessible or addressable memory locations.

Question 23

What is the benefit of increasing the address bus width from 16 bits to 32 bits?

Answer 23

A bus width of 16 bits can address 2^16 memory locations, whereas a bus width of 32 bits allows
2^32 memory locations to be simultaneously accessed.

Question 24

PROPERTIES OF THE DATA BUS

Answer 24

- It is a bi-directional bus (data can travel in both directions). - It sends data between the processor, the memory unit, and the input OR output devices that are currently being processed. - The data can be an address, an instruction, or a numerical value.

Question 25

PROPERTIES OF THE WIDTH OF THE DATA BUS

Answer 25

- The width of the data bus determines the number of bits that can be simultaneously transferred. - It improves processing speed and computer performance as fewer transfers are needed.

Question 26

PROPERTIES OF THE CONTROL BUS

Answer 26

- It is a bi-directional bus (signals can travel in both directions). - It carries control signals around the CPU and transmits timing signals to control all the components. - It carries signals to synchronize the fetch-execute cycle. - It is usually 8 bits wide, as there is no need for it to be any wider since it only carries control signals.

Question 27

How is an instruction fetched in a computer based on the Von Neumann model?

Answer 27

- The program counter (PC) holds the address of the instruction. - The address held in the program counter (PC) is sent to the memory address register (MAR). - The address is sent using the address bus. - The program counter (PC) is incremented. - The instruction is sent from the address in memory to the memory data register (MDR). - The instruction is transferred using the data bus. - The instruction is sent to the current instruction register (CIR).

Question 28

What's the component of the CPU that is responsible for decoding instructions?

Answer 28

Control Unit (CU)

Question 29

How is an instruction executed in a computer based on the Von Neumann model?

Answer 29

- The CPU passes the decoded instruction as a set of control signals using the control bus to the appropriate components within the computer system. - This allows each instruction to be carried out in its logical sequence.

Question 30

What is clock speed?

Answer 30

Clock speed is a factor that affects the performance of a PC by determining how fast instructions are processed.

Question 31

What happens during each clock pulse?

Answer 31

During each clock pulse, one instruction is executed, meaning one fetch–execute cycle is completed.

Question 32

How does clock speed affect the number of instructions executed per second?

Answer 32

Higher clock speed increases the number of instructions that can be executed per second.

Question 33

What is the effect of increasing the clock speed on fetch–execute cycles?

Answer 33

Increasing the clock speed increases the number of fetch–execute cycles that can be performed per second.

Question 34

How does clock frequency relate to execution time?

Answer 34

The higher the clock frequency, the shorter the execution time for each instruction.

Question 35

How does increasing clock frequency affect PC performance?

Answer 35

Increasing the clock frequency improves performance because instructions are executed more quickly.

Question 36

How does clock speed affect computer performance?

Answer 36

A higher clock speed means more Fetch—Decode—Execute cycles per second.

Question 37

How does the Number of Cores affect computer performance?

Answer 37

More cores mean more instructions can be carried out simultaneously.

Question 38

How does the Bus Width affect computer performance?

Answer 38

Increasing the width allows the transfer of more data each time and allows more memory locations to be directly accessed.

Question 39

How does the cache affect computer performance?

Answer 39

The higher the capacity of cache memory, the more frequently used instructions it can store for fast access.

Question 40

What is an instruction set?

Answer 40

- An instruction set is a list of all the commands that can be processed by a CPU, and the commands are machine code. - An example of an instruction set is the X86, a common CPU standard used in many modern computers.

Question 41

What is the difference between program code and instruction set?

Answer 41

- The instruction set is machine code instructions that instruct the CPU about how to carry out an operation. - The program code needs interpreters or compilers to convert the code into the instruction set understood by the computer.

Question 42

What is an embedded system?

Answer 42

An embedded system is a computer system used to perform a dedicated function.

Question 43

What does an embedded system contain?

Answer 43

An embedded system contains a microprocessor or microcontroller within a larger device to perform one specific task.

Question 44

What are examples of functions performed by embedded systems?

Answer 44

Embedded systems are used in domestic appliances, cars, security systems, lighting systems, and vending machines.

Question 45

How is an embedded system different from a general-purpose computer?

Answer 45

An embedded system performs one specific function, while a general-purpose computer, like a PC or laptop, is used to perform many different functions.

Question 46

Why is an embedded system integrated into a device?

Answer 46

An embedded system is integrated into a device to control its operations in a more efficient way.

Question 47

How can devices with embedded systems be controlled today?

Answer 47

Devices such as cookers, refrigerators, and central heating systems can now be activated using a web-enabled device like a mobile phone, computer, or tablet.

Question 48

What are 2 benefits + 2 drawbacks of embedded systems?

Answer 48

BENEFITS: - They are small in size and therefore easy to fit into devices. - They are relatively low-cost to make. DRAWBACKS: - It can be difficult to upgrade some devices to the latest technology. - The troubleshooting faults in the device becomes a specialist task.