Chapter 4 (Section 1) #7

Question 1

Section 1: CPU Architecture and Key Terms

Question 2

What are the 6 main components of the Von Neumann architecture?

Answer 2

1. Control Unit (CU)
2. Arethmetic and Logic Unit (ALU)
3. Immediate Access Store (IAS)
4. System clock
5. Buses
6. Registers

Question 3

What is the function of the Arithmetic and Logic Unit (ALU)?

Answer 3

The ALU is the component in the processor that carries out all arithmetic and logical operations while a program is running. It is possible for a computer to have more than one ALU.

Question 4

How are multiplication and division operations performed in the ALU?

Answer 4

They are carried out through sequences of addition, subtraction, and left or right shifting.

Question 5

What is the function of the Accumulator (ACC)?

Answer 5

It is a general-purpose register used to store numerical values temporarily at any part of a given operation or calculation.

Question 6

What is the role of the Control Unit (CU)?

Answer 6

It ensures the synchronization of data flow and programs by sending control signals along the control bus and interpreting instructions read from memory.

Question 7

What is the purpose of the System Clock?

Answer 7

It generates timing signals on the control bus to ensure synchronization and prevent system crashes.

Question 8

What is the Immediate Access Store (IAS)?

Answer 8

Holds the data and programs that the processor needs to access.
Acts as a faster alternative to read/write operations than backing up store.
Temporarily stores key data needed by an application to speed up operations.

[IT IS THE RAM IN THE VON NEUMANN ARCHITECTURE, NO SIMILAR THING FOR SECONDARY STORAGE AS CPU DOES NOT DIRECTLY ACCESS THE MAIN MEMORY]

Question 9

What is a Register in a processor?

Answer 9

A register is a temporary component that can be general or specific in use, holding data or instructions as part of the fetch-execute cycle.

Question 10

What are the definitions of General Purpose Registers and Special Purpose Registers?

Answer 10

1. General Purpose Registers: Holds data frequently used by the CPU. Can be accessed directly. Ex. Accumulator.
2. Special Purpose Registers: Have specific functions within the CPU and hold the program status. Ex. PC, MAR, IR

Question 11

Identify two differences between special purpose registers and general purpose registers.

Answer 11

1. Special purpose registers hold the status of the program whereas general purpose registers hold the temporary data used while preforming operations.
2. Special purpose registers are specialised for a specific use, whereas general purpose registers are used for any purpose.
3. General purpose registers can be used by most instrcutions, whereas special purpose registers can only be used by certain instructions.

Question 12

What is the Status Register (SR) used for?

Answer 12

It is used when an instruction requires arithmetic or logical processing, containing bits (flags) that are set or cleared based on the operation’s result.

Question 13

Define the following flags in the Status Register: Carry (C), Negative (N), Overflow (V) and Zero (Z).

Answer 13

1. Carry (C): Set to 1 if there is a carry after an addition.
2. Negative (N): Set to 1 if the result is negative (e.g., N=1).
3. Overflow (V): Set to 1 if an arithmetic operation results in an overflow.
4. Zero (Z): Set to 1 if the result of an operation is zero.

Question 14

How is clock speed measured and what does it represent?

Answer 14

It is measured in GHz.
It represents the vibrational frequency of the clock. For example, 3.5 GHz means 3.5 billion clock cycles per second.

Question 15

How does the clock speed affect the preformance of a computer.

Answer 15

1. Each instruction is executed on a clock pulse.
2. so the clock speed dictates the number of instructions that can be run per second.
3. The faster the clock speed the more instructions can be run per second

Question 16

What is “Overclocking” and what are its risks?

Answer 16

It is changing the clock speed to a value higher than the factory setting, which can enhance speed but cause overheating, instability, or crashes.

Question 17

What is a “Core” in a CPU?

Answer 17

A core is a unit consisting of an ALU, a control unit, and registers. A CPU can contain multiple cores (e.g., dual-core has two, quad-core has four) to distribute tasks.

Question 18

How does the number of cores in a computer affect its preformance.

Answer 18

1. Each core processes one instruction per clock pulse.
2. More/multiple cores mean that sequences of instructions can be split between them.
3. So more than one instruction is executed per clock pulse.
4. More cores decreases the time taken to complete task.

Question 19

Section 2: System Buses

Question 20

What is a System Bus?

Answer 20

A parallel transmission component used in computers where each wire transmits one bit of data.

Question 21

Describe the Address Bus.

Answer 21

It is a unidirectional bus that carries addresses throughout the computer system.

Question 22

How does the width of the Address Bus affect the system?

Answer 22

It determines the number of memory locations that can be directly addressed (e.g., 16-bit addresses 65,536 locations; 32-bit addresses over 4 billion).

Question 23

Describe the Data Bus.

Answer 23

It is a bidirectional bus that carries data between the processor, memory, and I/O (Input/Output) devices.

Question 24

Describe the Control Bus.

Answer 24

It is a bidirectional bus that carries signals from the control unit to all other computer components.

Question 25

Section 3: Computer Ports

Question 26

What is a Computer Port?

Answer 26

An external connection that allows a computer to communicate with peripheral devices.

Question 27

Define Universal Serial Bus (USB) and its data transmission type.

Answer 27

USB is a standard for connecting devices. It uses half-duplex serial data transmission, where bits are sent one after another using the sender's own clock.

Question 28

Describe the physical structure and operation of a USB connection.

Answer 28

USB cables are four-wired (two for power/earth, two for data). The computer detects a device via a voltage change on the data wires and then loads the appropriate driver.

Question 29

List two pros and two cons of USB technology.

Answer 29

Pros: Automatic device detection and backward compatibility. Cons: Limited transmission rate and a maximum cable length of about 5 meters.

Question 30

What are the features of HDMI?

Answer 30

It transfers uncompressed digital audio and video on a single cable, supports high-definition, widescreen formats, and fast refresh rates.

Question 31

What is Video Graphics Array (VGA)?

Answer 31

An older port technology supporting video only. It is easy to split signals but is becoming outdated.

Question 32

Section 4: Fetch-Execute Cycle and RTN

Question 33

Define the Fetch-Execute cycle.

Answer 33

It is the cycle in which instructions and data are retrieved from memory, decoded, and then executed by the CPU.

Question 34

What are the roles of the PC and CIR in the Fetch-Execute cycle?

Answer 34

• Program Counter (PC): Stores the address of the next instruction to be fetched. • Current Instruction Register (CIR): Holds the data received from the MDR. Stores the instruction currently being executed or decoded.

Question 35

Define the roles of the MAR and MDR.

Answer 35

• Memory Address Register (MAR): Stores the address of the memory location being read from or written to. • Memory Data Register (MDR): Stores data just read from memory or data about to be written to memory.

Question 36

What is Register Transfer Notation (RTN)?

Answer 36

A shorthand notation used to represent the movement of data and instructions in a processor during the fetch-execute cycle.

Question 37

Provide the RTN for the Fetch stage of the cycle.

Answer 37

1. MAR ← [PC] (The contents of the PC are copied into the MAR) 2. PC ← [PC] + 1 (The address in the PC is incremented) 3. MDR ← [[MAR]] (The data in the location pointed to by the MAR is copied to the MDR) 4. CIR ← [MDR] (The contents of the MDR are copied into the CIR)

Question 38

Describe the stages of the Fetch-Decode-Execute Cycle.

Answer 38

1. The address in the program counter is the address of the next item to be fetched. 2. The address is copied into the MAR using the address bus. 3. The instruction from that address moved/copied from main memory to MDR using the data bus. 4. The instruction is transferred from MDR to CIR. 5. The processor’s instruction set is used to decode the instruction// the instruction is decoded in the CIR ..into op code and operand. 6. The processor executes the instruction. 7. The address in the PC is incremented for the next loop.

Question 39

Section 5: Interrupts

Question 40

What is an Interrupt?

Answer 40

A signal sent from a device or software to the processor requesting its attention, causing the current process to pause.

Question 41

What is the Interupt Register?

Answer 41

A register that is set to 1 when an interupt is detected during the FDE cycle. Stored in the SR.

Question 42

What are the purpose of interupts?

Answer 42

1. Used to ensure that vital tasks are dealt with immediately. 2. Enables multitasking to be carried out on a computer.

Question 43

What is an Interrupt Service Routine (ISR)?

Answer 43

Software (also called an interrupt handler) that handles specific interrupt requests and sends them to the CPU for processing.

Question 44

What happens when an interupt is received?

Answer 44

1. The interupt is given a priority and placed in the interupt queue. 2. Processor finishes current Fetch-Decode-Execute cycle and checks the interupt register. 3. If the interupt is of lower priority, the processor continues with process. 4. If the interupt is of higher priority, the processor stores current process and registers on the stack in the memory. 5. The processor checks the source of the interupt and calls appropriate interupt service routine (ISR). 6. ISR handels the interupt. 7. The processor retrieves content of previous process and continues.

Question 45

Provide an example of a Hardware Interrupt and a Software Interrupt.

Answer 45

Hardware: Pressing a key on the keyboard or a printer "out of paper" message. Software: A program crashing due to division by zero.

Question 46

Identify the factors that can affect the performance of the computer system and state how each impacts performance.

Answer 46

Clock speed: higher clock speed means more FE cycles per second, so more instructions are executed per second. Number of cores: more cores mean more instructions can be carried out simultaneously, decreasing time taken to complete tasks. Bus width: a wider bus allows the transfer of more data each cycle // allows more memory locations to be directly addressed. Cache size: higher capacity cache means more frequently used instructions can be stored for fast access, reducing the need to fetch from slower RAM.