U4 Processor Fundamentals

Question 1

What is meant by the Von Neumann model?

Answer 1

• Uses a single processor
• Follows a linear sequence of fetch-decode-execute operations for the set of instructions; in order to do this, processor uses registers

Question 2

What is the stored program concept?

Answer 2

Both instruction and data are stored in the computer memory itself

Question 3

What are registers?

Answer 3

Smallest unit of storage of microprocessor; allows fast data transfer between other registers

Question 4

What are General purpose registers?

Answer 4

Used to temporarily store data values which have been read from memory or some processed result

Question 5

What are special purpose registers?

Answer 5

Only accessible by assembly language instructions and only holds either data or memory location(not both)

Question 6

What does a Program Counter do?

Answer 6

Holds address of next instruction to be fetched

Question 7

What does a Memory Data Register do?

Answer 7

Holds data value fetched from memory

Question 8

What does a Memory Address Register do?

Answer 8

Holds address of location of program which is to be accessed

Question 9

What does an Accumulator do?

Answer 9

Holds all values that are processed by arithmetic and logic operations

Question 10

What does an Index Register do?

Answer 10

Stores a number used to change an address value

Question 11

What does a Current Instruction Register do?

Answer 11

Once program instruction fetched, it is stored here and allows processor to decode and execute it

Question 12

What does a status register do?

Answer 12

Dedicated registers containing information about the intermediate states or outcomes of various processes in the processor.
e.g. indicates if calculation has produced overflow error

Question 13

What does the ALU do?

Answer 13

Processes instructions which require some form or arithmetic or logical operation

Question 14

What does the CU do?

Answer 14

Fetches instructions from memory, decodes them and synchronises operations before sending to computer memory, ALU and input output devices to direct how to respond to instructions sent to processor

Question 15

What does Immediate Store Access do?

Answer 15

Memory unit that can be directly accessed by a processor

Question 16

What does a System Clock do?

Answer 16

Timing device connected to processor that is needed to synchronise all components

Question 17

What are buses?

Answer 17

Set of parallel wires that allow carries data between components in a computer system

Question 18

What is a data bus?

Answer 18

Bi-directional bus that carries data instructions between processor, memory and I/O devices

Question 19

What is an address bus?

Answer 19

Unidirectional bus that carries address of main memory location or I/O device about to be used, from processor to MAR

Question 20

What is a control bus?

Answer 20

Bi-directional bus that is used to transmit control signals from CU to ensure access or use of data and address buses by components of system. doesn’t lead to conflict

Question 21

What is clock speed?

Answer 21

Number of pulses the clock sends out in a given time interval, which determines number of cycles CPU executes measured in Hz

Question 22

What happens if clock speed increases?

Answer 22

More cycles per unit time, increasing performance

Question 23

What is bus width?

Answer 23

Determines number or bits that can be simultaneously transferred

Question 24

What happens if bus width increases?

Answer 24

Increases number of bits transferred per unit time, increasing processing speed and performance

Question 25

What happens if cache memory is increased?

Answer 25

Cache memory stores commonly used instructions so more instructions can be stored and wait for CPU to wait for instructions to load decreases, so more cycles per unit time increasing performance

Question 26

What happens when number of cores increases?

Answer 26

Each core simultaneously processes different instructions so the more cores, the faster processing time is, so performance is increased

Question 27

What are ports?

Answer 27

Hardware which provides a physical interface between a device with CPU and a peripheral device - this is done because peripheral devices can’t directly connect to CPU

Question 28

What is USB?

Answer 28

Universal Serial Bus can connect both input and output devices to processor through USB port

Question 29

What is HDMI?

Answer 29

High definition multimedia interface can only connect output devices to processor through HDMI port
Transmits high bandwidth and high resolution video and audio streams

Question 30

What is VGA?

Answer 30

Video Graphics Array can only connect output devices to processor through VGA port

Question 31

What are the steps in the fetch-decode-execute cycle?

Answer 31

• PC holds next instruction to be executed
• Address in PC copied to MAR
• PC is incremented
• Instruction loaded to MDR from address held in MAR
• Instruction from MDR loaded to CIR
• Decode: Opcode and operand parts of instruction identified
• Execute: Instructions executed by CU sending control signals

Question 32

What is an interrupt?

Answer 32

Signal from a program seeking CPU’s attention

Question 33

What is the ISR and what does it do?

Answer 33

The interrupt service routine handles the interrupt by controlling the CPU
different ISRs used for different sources of interrupt

Question 34

What is Assembly language?

Answer 34

Low-level programming language with instructions made up of an opcode and an operand

Question 35

What is machine code?

Answer 35

Code written in binary that uses processor’s basic machine operations - every assembly language instruction translates into exactly one machine code instruction

Question 36

What is symbolic addressing?

Answer 36

Symbols can be used to represent opcodes, labels can be used for addresses

Question 37

What is absolute addressing?

Answer 37

Fixed address in memory

Question 38

What is an assembler?

Answer 38

Software that changes assembly language into machine code for processor to understand

Question 39

What happens on the first pass of a two-pass assembler?

Answer 39

Symbol table created to enter symbolic addresses and labels into specific addresses
Errors suppressed

Question 40

What happens on the second pass of a two-pass assembler?

Answer 40

Jump instructions access memory addresses via table
Whole source code translates into machine code