Unit 2 - Chapter 5

Question 1

Functional Units

Answer 1

It is important to study computers as collections of functional units or subsystems that perform tasks such as instruction procession, information storage, computation and data transfer.

Question 2

Computer organization

Answer 2

the branch of computer science that studies computers in terms of their major functional units.

Question 3

Reminder about transistors

Answer 3

transistors are grouped into gates, and gates into circuits

Question 4

Von Neumann Architecture

Answer 4

the structure and organization of virtually all modern computers are based on a single theoretical model of computer design called the Von Neumann Architecture

Question 5

Von Neumann

Answer 5

created programing as we know today by proposing the design for a stored program computer in 1946

Question 6

The Von Neumann Architecture is based the following three characteristics.

Answer 6

• Four Major subsystems called memory, input/output, arithmetic/logical unit ( ALU), and the control unit. The ALU and the control unit are often bundled together in what is called the Central Processing Unit ( or CPU).
• The stored program concept, in which the instructions to be executed by the computer are represented as binary values and stored in memory.
• The sequential execution of instructions, in which one instruction at a time is fetched from memory and passed to the control unit, where it is decoded and executed.

Question 7

Memory

Answer 7

the functional unit of a computer that stores and retrieves the instructions and the data being executed.

Question 8

Random Access Memory ( RAM)

Answer 8

Computer memory uses an access technique called random access and the memory unit is frequently referred to as random access memory ( RAM)

Question 9

Characteristics of RAM

Answer 9

• • Memory is divided into fixed-size units called cells
• ** Each cell is associated with a unique identifier called an address.
• ** All accesses to memory are to a specified address, and we must always fetch and store a complete cell _ that is, all the bits in that cell. The cell is the minimum unit of access. The time it takes to fetch or store the contents of a cell is the same for all the cells in memory.

Question 10

Read-Only memory ( ROM)

Answer 10

Random access memory into which information has been prerecorded during manufacture. This information cannot be modified or removed, only fetched. ROM is used to hold important system instructions and data in a place where a user cannot accidentally or intentionally overwrite them.

Question 11

The cell size

Answer 11

the number of bits per cell also called the memory width.

Question 12

The value 2^n is called

Answer 12

the maximum theoretical memory size or the address space of the computer

Question 13

2^n representas

Answer 13

the maximum theoretical memory size; a computer with N address bit does not necessarily come equipped with 2^n memory cells. It simply means that its memory can be expanded to 2^n

Question 14

When dealing with memory, it is important to keep in mind the distinction between

Answer 14

an address and the contents of that address.

Question 15

The 2 basic memory operations are

Answer 15

fetching and storing

Question 16

value = Fetch ( address) meaning…

Answer 16

Fetch a copy of the contents of the memory all with the specified address and return those contents as the result of the operation. The original contents of the memory cell that was accessed and unchanged. This is called a nondestructive fetch.

Question 17

Store ( address,value) meaning…

Answer 17

Store the specified value into the memory cell specified by the address. The previous contents of the cell are lost. This is termed a destructive store.

Question 18

In RAM => The time to carry either a fetch or a store operation

Answer 18

is the same for all 2^n addresses.

Question 19

Fetching and store are only allowed

Answer 19

to an entire cell. The cell is the minimum accessible unito of memory.

Question 20

If we want to modify a single bit of memory…

Answer 20

we first need to fetch the entire cell containing that bit, change the one bit, and then store the entire cell.

Question 21

Memory Addresses

Answer 21

used to implement the fetch and store operations

Question 22

Memory Address Register(MAR)

Answer 22

Holds the address of the cell to be accessed

Question 23

Memory Data Register ( MDR)

Answer 23

contains the data value being fetched or stored.

Question 24

Row and Selection lines to access

Answer 24

The first two binary digits of the addresses are identical to the row number. The last two binary digits of the addresses are identical to the column number.

Question 25

Fetch/store controller

Answer 25

controls whether memory does a fetch or a store operation

Question 26

Cache memory

Answer 26

The first time that the computer references a piece of data, it should copy that data from regular RAM memory to a special high speed memory unit called cache memory. It should also copy the contents of the memory cells located near this item into the cache. A cache is typically 5 to 10 times faster than RAM but much smaller —- on the order of a few megabytes rather than gigabytes. This limited size is not a problem because the computer does not keep all of the data there, the those items that were accessed most recently and that, presumably will be needed again immediately.

Question 27

Principle of Locality

Answer 27

When the computer uses something, it will probably use it again very soon, and it will probably use the neighbours of this item very soon.

Question 28

Cache bit rate

Answer 28

The information we need is in the cache i.e 70% of the time. A higher cache hit rate can lead to even greater savings.

Question 29

Input/Output ( I/O)

Answer 29

the devices that allow a computer system to communicate and interact with the outside world as well as store information

Question 30

Volatile memory

Answer 30

the information disappears when the computer is turned off

Question 31

Nonvolatile storage

Answer 31

is the role of mass storage systems such as disks and tapes

Question 32

Input/Output controller

Answer 32

An I/O controller is like a special-purpose computer whose responsibility is to handle the details of input/output and to compensate for any speed differences between I/O devices and other parts of the computer.

Question 33

Interrupt signal

Answer 33

A special hardware signal for when an I/O operation is done.

Question 34

Defragmenting a disk

Answer 34

to reorganize files on the disk so that many pieces of the file as possible are stored in sectors on the same track, regardless of the surface it is on. If many pieces of the file are on the same track, then no movement of the read head arm is required and seek time is 0.

Question 35

Arithmetic/Logic Unit ( ALU)

Answer 35

the subsystem that performs such mathematical and logical operations as addition, subtraction, and comparison for equality.

Question 36

Processor ( CPU)

Answer 36

The integrated ALU and control unit

Question 37

Data path

Answer 37

the registers, the interconnections between components and the ALU circuitry.

Question 38

Register

Answer 38

a storage cell that holds the operations of an arithmetic operation and that, when the operation is complete holds its results.

Question 39

BUS

Answer 39

A patch for electrical signals ( think of this as a wire)

Question 40

stored program

Answer 40

a sequence of machine learning instructions stored as binary values in memory

Question 41

Control Unit Tasks

Answer 41

1) Fetch from memory the next instructions to be executed
2) Decode it - determine what is to be done
3) Execute it - by issuing the appropriate command to the ALU memory or I/O controllers

Question 42

Instruction set

Answer 42

The set of all operations that can be executed by a proccessor

Question 43

Machine language instructions can be grouped into four basic classes called

Answer 43

data transfer, arithmetic, compare and branch

Question 44

Data Transfer

Answer 44

These operations move information between or within the different components of the computer. For example: memory cell -> ALU register

Question 45

Arithmetic

Answer 45

These operations cause the arithmetic/logic unit to perform a computation. Typically, they include arithmetic operations like +,-,x, and /, as well as logical operators such as AND, OR, and NOT. Depending on the instruction set, the operands may reside in memory or they may be in an ALU register.

Question 46

Compare

Answer 46

These operations compare two values and set an indicator on the basis of the results of the compare

Question 47

Branch

Answer 47

These operations alter the normal sequential flow of the control. The normal mode of operation of a Von Neumann machine is sequential. The branch instructions disrupt this sequential mode.

Question 48

Vectors

Answer 48

A vector V is simply a collection of values

Question 49

SIMD parallel processing

Answer 49

( Single instruction/multiple data stream )

Question 50

MIMD parallel processing

Answer 50

( Multiple Instruction Stream/ multiple data stream) also called cluster computing

Question 51

Parallel Algorithms

Answer 51

the study of techniques that makes efficient use of parallel architectures.