Structure and Role of a Processor

Question 1

Arithmetic Logic Unit

Answer 1

ALU performs arithmetic and logic operations
math operations plus AND, OR and XOR

Question 2

Control Unit

Answer 2

responsible for controlling various components of the processor
controls fetch execute cycle

Question 3

Registers

Answer 3

Small storage locations that hold data temporarily
have high read/write speeds

Question 4

General Purpose registers

Answer 4

used as storage for any data that is required by instructions during execution

Question 5

Special Purpose Registers

Answer 5

assigned to the storage of specific information
include Program counter, current instructions reigster, memory address register, memory buffer register and status register

Question 6

Program Counter

Answer 6

holds the memory address of the next instruction to be executed in fetch/execute cycle

Question 7

Current instruction register

Answer 7

holds the instruction that is currently being executed by the processor

Question 8

Memory address register

Answer 8

stores the memory address of a memory location that is to be read from/written to

Question 9

Memory buffer register

Answer 9

holds the contents of a memory location that has been read from or data that is to be stored

Question 10

Status register

Answer 10

contains a number of bits the values of which can change to indicate the occurrence of an interrupt

Question 11

Clock

Answer 11

Inside a computers processor is the system clock
generates a timing signal which changes at a regular frequency
synchronises communication between components of the processor

Question 12

Fetch decode execute cycle

Answer 12

is a continuous cycle performed by the processor
contains 3 stages

Question 13

Fetch (first stage)

Answer 13

the next instruction to execute is retrieved from main memory
content of PC is copied to the MAR
content of MAR is transferred to main mem of address bus
instruction is sent from main mem to MBR by data bus
PC is incremented by one
content of MBR is copied to the CIR

Question 14

Decode (stage 2)

Answer 14

the content of the CIR is decoded by the control unit
decoded instruction is split into either opcode or operands

Question 15

Execute

Answer 15

any data required by instruction that isnt present in registers is fetched
instruction is carried out
results of any calcs are stored in GP registers or main mem

Question 16

Checking for interrupts

Answer 16

b/ween each fetch-execute stage of cycle, content of status register is checked for changes that could signify the occurrence of an interrupt

Question 17

Opcode

Answer 17

type of operation that is to be carried out
e.g. addition/subtraction

Question 18

Operands

Answer 18

are pieces of data on which operation is performed

Question 19

Addressing modes

Answer 19

one bit in machine code is assigned to the addressing mode in use (immediate and direct)

Question 20

Immediate addressing

Answer 20

value specified in operand is to be treated as actual value

Question 21

Direct addressing

Answer 21

value specified by operand signifies a memory address

Question 22

Factors affecting processor performance

Answer 22

number of cores
cache memory
clock speed
word length
address bus width
data bus width

Question 23

Number of cores

Answer 23

directly affects performance of processor
each core can perform its own fetch-execute cycle independetly of others
so different applications can be allocated different cores

Question 24

Cache memory

Answer 24

small portion of incredibly fast mem
read/write speads far higher than HDD and SSD
used to store frequently used info and reduces time fetching same info from main mem time

Question 25

Clock speed

Answer 25

processors clock speed relates to frequency pulses generated by the system ^frequency = more cycles of fetch-execute cycle done - errors can occur when a computers clock is increased too far

Question 26

Word Length

Answer 26

a word is a group of bits that is treated as a single unit by a processor can represent both instructions and data length of a word is the number of bits assigned to it higher word lengths allow for more bits to be transferred and manipulated as a single unit

Question 27

address bus width

Answer 27

width of a bus relates to number of parallel wires that make up the bus increasing width of address bus increases range of addresses that it can specify - increases the computers amount of addressable memory

Question 28

Data bus width

Answer 28

increasing width increases volume of data that can be transferred over the bus at any one time wider data bus allows processor to fetch more data from main mem in one cycle of fetch execute cycle reducing no. of cycles required to fetch large volumes of data