CS1 week 5 flashcards (MARIE, CPU, Memory...)

Question 1

What is the main role of cpu

Answer 1

driving force of fetch, decode, execute instructions (cycle)

Question 2

What are the 2 principle parts of the cpu

Answer 2

. The datapath
.The control unit

Question 3

What does the datapath consist of

Answer 3

It consists of the ALU and registers which are connected to each other and to memory by data bus

Question 4

What are registers

Answer 4

specialised forms of memory that has specific data stored inside it

Question 5

Why are registers fast?

Answer 5

They are close in proximity to cpu

Question 6

What does the control unit do

Answer 6

send signals to activate various components
to perform sequenced operations
.ensure instructions are fetched, decoded and executed in correct sequence

Question 7

How is computer memory ordered

Answer 7

A linear array of addressable storage cells

Question 8

What is a word

Answer 8

A storage cell of memory of fixed size

Question 9

what does word addressable mean

Answer 9

cpu identifies specific storage cells (words) to read and write data to and from memory

Question 10

what does it mean by byte addressable

Answer 10

cpu identifies data by bytes -smaller parts (usually half) of a word- eg if a word is 16 bits processor may identify particular 8 bits of memory rather than the word

Question 11

How many memory locations is 4M X 16 Ram chips

Answer 11

4 x 2^20 16 bit memory locations
. M - 2^20
. 16 part of 4Mx 16 tells you no of bits

Question 12

What are the 2 ways io devices can be connected 2 cpu through interfaces

Answer 12

. Memory mapped
.Instruction mapped

Question 13

What does it mean by memory mapped

Answer 13

There is a reserved section of memory for input and output devices through which CPU interacts

Question 14

What does it mean by instruction mapped

Answer 14

CPU has specific instructions for controlling i/o devices

Question 15

what is a bus

Answer 15

An array of wires that simultaneously transmit a single bit along each line

Question 16

What does an address bus/ line do

Answer 16

sends a memory address along the bus from the cpu to the RAM to specify the location in memory where data should be fetched or written to
.uni directional

Question 17

What does the data bus do?

Answer 17

. conveys bits from one device to another
sends data to and from memory

Question 18

control bus/ lines

Answer 18

determines the direction of data flow and when each device can access the bus

Question 19

What does a clock do

Answer 19

synchronises activities of its various components

Question 20

What is the cpu time equation

Answer 20

T = seconds / program X no of cycle / instruction X seconds/ cycle

Question 21

What do interrupts do

Answer 21

.Alter the normal flow of execution of a program when an event of higher priority occurs
. There are procedures that directs the cpu on actions to take when an interrupt occurs to handle event

Question 22

What is an example of an interrupt event

Answer 22

i/ o requests
operational errors (dividing by 0)
invalid instructions

Question 23

What does Accumulator AC register do

Answer 23

16 bit register that hold data cpu will process

Question 24

what does the MAR do

Answer 24

12 bit register the hold memory address of data referenced

Question 25

what does MBR do

Answer 25

16 bits - hold data that has just been read from memory or is about to be written to memory

Question 26

program counter

Answer 26

12 bit- holds the address of the next instruction to be executed

Question 27

Instruction register

Answer 27

16 bit- holds instruction immediately before its execution

Question 28

Input register (IN)

Answer 28

8 bit - holds data read from input device

Question 29

output register

Answer 29

8 bit- holds data to be written to output device

Question 30

How are registers connected

Answer 30

all of registers connected to each other and memory via a common data bus

Question 31

what does the ISA (intruction set architecture)

Answer 31

specifies formate of instructions and operations the machine can perform
. is an interface between software and hardware