computer organizaiton (week 3)

Question 1

what is a program

Answer 1

program is a source file that contains many lines of instructions.

it is written in a high level programming language such as C, java, python

Question 2

how are programs executed

Answer 2

high level language –> low level language (assembly language) –> machine language(binary)

Question 3

computers execute ______

Answer 3

machine language

Question 4

What is the von Neumann architecture

Answer 4

Has a fixed set of electronic parts, which can be manipulated to perform various tasks determined by a variable program.

The parts are:
- cpu
- primary memory unit
- collection of I/O devices
- buses to interconnect the components

Question 5

what does the CPU contain?

Answer 5

ALU
control unit

Question 6

what does the ALU do

Answer 6

–> responsible for performing artihmetic and logical operations

Question 7

ALU comprises of ?

Answer 7

–> comprises of functional unit that performs operations

–> registers that loads and saves data to and from the primary memory. 32 to 64 bit registers to hold 32-bit data

Question 8

how are computations accomplished in ALU

Answer 8

–> Loading binary values into registers
–> performing operations on the registers using the function unit
–> storing the result back into a general register
–> saving the register contents back into memory

Question 9

what is the control unit

Answer 9

causes a sequence of instruction to be stored in memory to be retrieved

Question 10

what does the control unit comprise of?

Answer 10

fetch unit
decode unit
execute unit
instruction registrar
program counter register

Question 11

control unit works based on the __________ cycle

Answer 11

fetch execute cycle

Question 12

what is fetch unit

Answer 12

fetches an instruction from memory

Question 13

what is decode unit

Answer 13

decode an instruction

Question 14

what is execute unit

Answer 14

signals ALU to execute instruction

Question 15

what is instruction registrar

Answer 15

contains a copy of the current instruction

Question 16

what is program counter registrar (PCR)

Answer 16

contains the memory address of the next instruction the unit is to load.

Question 17

What happens in the fetch phase of the control unit operation

Answer 17

Instructions are retrieved from the memory

Question 18

What happens during the execute phase of the control unit

Answer 18

ALU operations start happening

Cause memory data reference, I/O operations

Question 19

What is the primary memory unit

Answer 19

Stores both programs and data while they are being operated on by the cpu

Question 20

Interface between memory and cpu consists of _______ registers

Answer 20

3

Question 21

What are the 3 interfaces that memory and cpu interface consist of

Answer 21

Memory address register
Memory data register
Command register

Question 22

Primary memory unit is also referred to as

Answer 22

Random access memory

Question 23

How does primary memory unit store data

Answer 23

Stores programs and data in binary format

Question 24

What is the memory address register

Answer 24

Stores addresses of data to be read from or written to

Question 25

What is memory data register

Answer 25

Stores data that is read or to be written

Question 26

What is command register

Answer 26

Stores the command to be executed

Question 27

How does the primary memory work

Answer 27

Load mar with data

Load command with read
Data will appear in mdr

Question 28

What is device controller

Answer 28

Each device is controlled by a device controller

The device controller connects the device to the computers’ address and data bus

Provides an interface that the OS (device manager) can use to manipulate the device

Question 29

______ varies among controllers

Answer 29

interface

Question 30

OS provides ______ to hide the differences from the programmer

Answer 30

abstractions

Question 31

what does the device driver provided by controller do ?

Answer 31

Allows the OS to operate and synchronize its behaviour with the device operation

Question 32

how to determine when the I/O is complete

Answer 32

2 ways:
polling
Interrupt

Question 33

what does the device controller include as part of the interface

Answer 33

data registeres
command registers
status flags which includes done, busy or error

Question 34

what is polling

Answer 34

–> simplest way to keep polling the device to see the state of the I/O

–> device implements the status of the device as a flag

–> If the I/O is not done, the CPU executes a busy wait command to wait for the I/O to end, but the CPU is effectively waiting and doing nothing

Question 35

what is the advantage of polling

Answer 35

it is a simple implementation

Question 36

what is the disadvantage of polling

Answer 36

waste of CPU resource

Question 37

what is interrupt

Answer 37

–> CPU implements an interrupt request flag

–> when the device IO is completed, the device sets the interrupt request flag to signal the end of the IO

–> CPU, on its fetch cycle, would detect the flag and proceed to execute a set of routines to service the IO

Question 38

what is advantage of interrupt

Answer 38

minimize the cpu idle time

no need to keep polling the device

Question 39

what is the disadvantage of interrupt

Answer 39

complex implementation

Question 40

what is dma

Answer 40

dma stands for direct access memory and it allows data transfer between I/O devices and memory without CPU intervention.

cpu can start a dma block transfer and then
perform other work in parallel with the DMA
operation. This can significantly increase the
machine’s I/O performance.w