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Samsung Unveils Windows Devices

2012-08-30T23:56:00.007-07:00

Samsung ATIV S: World's
first Windows 8-powered smartphone

Nokia may be Microsoft’s partner on Windows phone hardware, but Samsung got the jump on its competitors by announcing the first handset to run Windows 8.

The ATIV S, Samsung announced Thursday, sports a 4.8-inch screen, a 1.5GHz dual-core processor and is just one-third of an inch thick.

The phone also has NFC and Bluetooth support, 1GB of onboard RAM, an 8 MP rear-facing and 1.9 MP front-facing camera, as well as the the option for 16 GB or 32 GB of internal storage. The phone also has a slot for an SD card.

Samsung has made a big deal, too, out of the phone’s battery — a key component if it’s going to be able to power that screen for the whole day.

In a post announ cing the phone over at Microsoft, Windows Phone marketing director Ben Rudolph also said that the phone’s design, which has a rounded bezel that tapers toward the back, make the phone very comfortable to hold.

The ATIV S also has an actual Windows button instead of a capactitive one, a design choice that bucks the mold a bit in the consumer tech world’s seeming war against physical buttons.

The ATIV S is flat-out beautiful, and it has the guts to match. But what’s impressed me most about the ATIV S is Samsung’s attention to detail. To get to your Start screen, you hit a raised physical Windows button, not a capacitive one. The speaker bar on the front and the back, as well as all of the buttons, are aluminum, not plastic. And the display glass has just the slightest of rounded edges. It all adds up to a device that looks great, feels great, and performs great.

The wait is over: Samsung unveils Galaxy Note II with Jelly Bean

2012-08-29T20:56:00.002-07:00

“I am pretty confident it will even outsell its predecessor,” said JK Shin, Samsung’s chief of mobile business.

Samsung has sold some 10 million of its original Galaxy Note devices, creating a new product category which has smaller screen than tablets, but bigger than smartphones.

Samsung hopes the new device will take the focus away from its loss of the court case. Apple is now seeking speedy bans on the sale of eight Samsung phones, moving swiftly to turn legal victory into tangible business gain.

The Galaxy Note phablet, one of the most popular Samsung devices after its flagship Galaxy S, is not included in the list of the potential US sales ban, and Samsung hopes the phablet upgrade will lift any post-Apple gloom at the South Korean group.

“There won’t be huge innovative changes in design, but the Note II will feature quite a few improvements and enable Samsung to carry on its strong sales momentum in the category,” said Lee Sun-tae, an analyst at NH Investment & Securities. “With the launch, Samsung will also be trying to turn around downbeat sentiment after the US legal defeat.”

Specs wise, it has a 1.6 GHz quad core processor, 2GB Ram, 3,100m Ahbattery , an 8 megapixel rear-facing and a 1.9 MP front-facing cameras with HD video recording.

It comes in HSPA Plus or 4G LTE connectivity versions, and 16 GB, 32 GB, and 64 GB tiers with expandable micro SD memory slot

A few interesting software features were shown off, such as Best Faces which allows users to choose the most preferred face or pose of each person from group portrait photos, and Smart Stay, which uses the camera to prevent the device from going into standby mode when it detects a user in front of the device.

The new version of the Note will feature a thinner and slightly bigger 5.5-inch screen, powerful quad-core processor, the latest version of the Android operating system called Jellybean, and improved stylus function.

“The Galaxy Note II is a strong successor to its surprise hit predecessor. Its clear differentiation is a big advantage in a congested fourth quarter market,” said CCS Insight analyst Geoff Blaber.

DATABASE MANAGEMENT SYSTEM

2012-05-18T01:07:00.000-07:00

Concept of Normalization

Purpose of Normalisation

Redundancy and Data Anomalies

Functional Dependency

Transitive Dependency

Stages of Normalisation

Purpose of Normalisation

1. To avoid redundancy by storing each ‘fact’ within the database only once.

2. To put data into a form that conforms to relational principles (e.g., single valued attributes, each relation represents one entity) - no repeating groups.

3.To put the data into a form that is more able to accurately accommodate change.

4.To avoid certain updating ‘anomalies’.

5.To facilitate the enforcement of data constraints.

Redundancy and Data Anomalies

Redundant data is where we have stored the same ‘information’ more than once. i.e., the redundant data could be removed without the loss of information.

Example: We have the following relation that contains staff and department details:

staffNo job dept dname city

SL10 Salesman 10 Sales Stratford

SA51 Manager 20 Accounts Barking

DS40 Clerk 20 Accounts Barking

OS45 Clerk 30 Operations Barking

the redundency in table could lead to following anamolies:

Insert Anomaly: We can’t insert a dept without inserting a member of staff that works in that department

Update Anomaly: We could change the name of the dept that SA51 works in without simultaneously changing the dept that DS40 works in.

Deletion Anomaly: By removing employee SL10 we have removed all information pertaining to the Sales dept.

Functional Dependency

Formal Definition: Attribute B is functionally dependant upon attribute A (or a collection of attributes) if a value of A determines a single value of attribute B at any one time.

Formal Notation: A ® B This should be read as ‘A determines B’ or ‘B is functionally dependant on A’. A is called the determinant and B is called the object of the determinant.

Example:

staffNo job dept dname Functional Dependencies

SL10 Salesman 10 Sales staffNo ® job

SA51 Manager 20 Accounts staffNo ® dept

DS40 Clerk 20 Accounts staffNo ® dname

OS45 Clerk 30 Operations dept ® dname

Compound Determinants: If more than one attribute is necessary to determine another attribute in an entity, then such a determinant is termed a composite determinant.

Full Functional Dependency: Only of relevance with composite determinants. This is the situation when it is necessary to use all the attributes of the composite determinant to identify its object uniquely.

Example:

order# line# qty price Full Functional Dependencies

A001 001 10 200 (Order#, line#) ® qty

A002 001 20 400 (Order#, line#) ® price

A002 002 20 800

A004 001 15 300

Partial Functional Dependency: This is the situation that exists if it is necessary to only use a subset of the attributes of the composite determinant to identify its object uniquely

Example:

student# unit# room grade Full Functional Dependencies

9900100 A01 TH224 2 (student#, unit#) ® grade

9900010 A01 TH224 14

9901011 A02 JS075 3 Partial Functional Dependencies

9900001 A01 TH224 16 unit# ® room

Repetition of data!

Transitive Dependency:A transitive dependency exists when there is an intermediate functional dependency.

Formal Notation: If A ® B and B ® C, then it can be stated that the following transitive dependency exists: A ® B ® C

Example:

staffNo job dept dname Transitive Dependencies

SL10 Salesman 10 Sales staffNo ® dept

SA51 Manager 20 Accounts dept ® dname

DS40 Clerk 20 Accounts

OS45 Clerk 30 Operations staffNo ® dept ® dname

here also Repetition of data!

Normalization Achieves This!

remove repeating groups and avoid redundancy and data anomalies by remoting partial and transitive functional dependencies.

Unnormalised Normal Form (UNF)

Definition: A relation is unnormalised when it has not had any normalisation rules applied to it, and it suffers from various anomalies.

First Normal Form (1NF)

Definition: A relation is in 1NF if, and only if, all its underlying attributes contain atomic values only.

Second Normal Form (2NF)

Definition: A relation is in 2NF if, and only if, it is in 1NF and every non-key attribute is fully dependent on the primary key.

Remove partial functional dependencies into a new relation

consider the relation

student( Rollno, Name, CourseNo, CourseName, Deptid, DeptName)

here {Rollno,,courseNo,Deptid} is candidate key

if there exist the partial functional dependency like Rollno-->Name or Deptid-->DeptName it is not in 2NF

Decomposition

student(Rollno,CourseNo,CourseName,Deptid)

X1(Rollno,Name)

X2(Deptid,DeptName)

Third normal form(3NF)

A relation R is in 3rd normal form if and only if it is in 2NF and every non-key attribute is non-transitively dependent on the primary key.

Remove transitive functional dependencies into a new relation

consider the relation

Shipdetails(Ship,Capacity,Date,Cargo,Value) with following functional dependency

Ship,Date-->Cargo,Capacity

Cargo-->Value relation is not in 3NF

Decomposition

Shipdetails(Ship,Capacity,Date,Cargo)

X1(Cargo,Value)

A relation in 3NF does not have any anamolies but it still have redundency.

Boyce-Codd Normal Form (BCNF)

A more restricted version of 3NF (known as Boyce-Codd Normal Form) requires that the determinant of every functional dependency in a relation be a superkey - for every FD: X => Y, X is a superkey

Consider the following relation:

STU-MAJ-ADV (Student-Id, Major, Advisor)

Advisor --> Major , but Advisor is not a superkey

Decomposition

STU-ADV (Student-Id, Advisor)

ADV-MAJ (Advisor, Major)

4th Normal Form

A Boyce Codd normal form relation is in fourth normal form if

(a)there is no multi value dependency in the relation or

(b)there are multi value dependency but the attributes, which are multi valued dependent on a specific attribute, are independent each other.

consider the following relation

Employee (Eid, Languages, Skills)

Eid --->> Languages Eid --->> Skills
Languages and Skills are independent.

Decomposition

Emplyee_Language(Eid, Languages)

Emplyee_Language(Eid, Skills)

What is a Transaction?

n A logical unit of work on a database

n An entire program

n A portion of a program

n A single command

n The entire series of steps necessary to accomplish a logical unit of work

n Successful transactions change the database from one CONSISTENT STATE to another

(One where all data integrity constraints are satisfied)

Example of a Transaction

n Updating a Record

n Locate the Record on Disk

n Bring record into Buffer

n Update Data in the Buffer

n Writing Data Back to Disk

ACID Properties of a Transaction

n Atomic – All or Nothing

All parts of the transaction must be completed and committed or it must be aborted and rolled back

n Consistency

The consistency property ensures that any transaction will bring the database from one valid state to another. Any data written to the database must be valid according to all defined rules, including but not limited to constraints, cascades, triggers, and any combination thereof.

n Isolation

The final effects of multiple simultaneous transactions must be the same as if they were executed one right after the other .

n Durability

If a transaction has been committed, the DBMS must ensure that its effects are permanently recorded in the database (even if the system crashes)

Transaction Management with SQL

n SQL Statements à Commit / Rollback

n When a transaction sequence is initiated it must continue through all succeeding SQL statements until:

!A Commit Statement is Reached

!A Rollback Statement is Reached

!The End of the Program is Reached (Commit)

!The Program is Abnormally Terminated (Rollback)

Transaction Log

n Keeps track of all transactions that update the database

n Record for the beginning of the transaction

n Type of operation (insert / update / delete)

n Names of objects/tables affected by the transaction

n Before and After Values for Updated Fields

n Pointers to Previous and Next Transaction Log Entries for the same transaction

n The Ending of the Transaction (Commit)

n Used for recovery in case of a Rollback

Concurrency Control

n Coordination of simultaneous transaction execution in a multiprocessing database system

n Ensure transaction serializability in a multi-user database

n Lack of Concurrency Control can create data integrity and consistency problems:

n Lost Updates

n Uncommitted Data

n inconsistent Retrievals

Serial Execution of Transactions

n Serial Execution of transaction means that the transactions are performed one after another.

n No interaction between transactions - No Concurrency Control Problems

n Serial Execution will never leave the database in an inconsistent state à Every Serial Execution is considered correct (Even if a different order would cause different results)

Serializability

n If 2 Transactions are only reading data items – They do not conflict à Order is unimportant

n If 2 Transactions operate (Read/Write) on Separate Data Items

– They do not conflict à Order is unimportant

n If 1 Transaction Writes to a Data Item and Another Reads or Writes to the Same Data Item à The Order of Execution IS Important

The Scheduler

n Special DBMS Program to establish the order of operations in which concurrent transactions are executes

n Interleaves the execution of database operations to ensure:

Serializability

Isolation of Transactions

n Bases its actions on Concurrency Control Algorithms (Locking / Time Stamping)

n Ensures the CPU is used efficiently (Scheduling Methods)

n Facilitates Data Isolation à Ensure that 2 transactions do not update the same data at the same time

Concurrency Control Algorithms

n Locking

A Transaction “locks” a database object to prevent another object from modifying the object

n Time-Stamping

Assign a global unique time stamp to each transaction

n Optimistic

Assumption that most database operations do not conflict

Locking

n Lock guarantees exclusive use of data item to current transaction

n Prevents reading Inconsistent Data

n Lock Manager is responsible for assigning and policing the locks used by the transaction

Locking Granularity

Indicates the level of lock use

n Database Level – Entire Database is Locked

n Table Level – Entire Table is Locked

n Page Level – Locks an Entire Diskpage

(Most Frequently Used)

n Row Level – Locks Single Row of Table

n Field Level – Locks a Single Attribute of a Single Row (Rarely Done)

Types of Locks:

n Binary Locks – Lock with 2 States

n Locked – No other transaction can use that object

n Unlocked – Any transaction can lock and use object

All Transactions require a Lock and Unlock Operation for Each

Object Accessed (Handled by DBMS)

n Eliminates Lost Updates

n Too Restrictive to Yield Optimal Concurrency Conditions

Shared / Exclusive Locks:Indicates the Nature of the Lock

n Shared Lock – Concurrent Transactions are granted READ access on the basis of a common lock

n Exclusive Lock – Access is reserved for the transaction that locked the object

n 3 States: Unlocked, Shared (Read), Exclusive (Write)

n More Efficient Data Access Solution

n More Overhead for Lock Manager

n Type of lock needed must be known

n 3 Operations:

nRead_Lock – Check to see the type of lock

nWrite_Lock – Issue a Lock

nUnlock – Release a Lock

n Allow Upgrading / Downgrading of Locks

Problems with Locking

n Transaction Schedule May Not be Serializable

n Can be solved with 2-Phase Locking

n May Cause Deadlocks

n A deadlock is caused when 2 transactions wait for each other to unlock data

Two Phase Locking

n Defines how transactions Acquire and Relinquish Locks

!Growing Phase – The transaction acquires all locks (doesn’t unlock any data)

!Shrinking Phase – The transaction releases locks (doesn’t lock any additional data)

n Transactions acquire all locks it needs until it reaches locked point

n When locked, data is modified and locks are released

Deadlocks

n Occur when 2 transactions exist in the following mode:

T1 = access data item X and Y

T2 = Access data items Y and X

If T1 does not unlock Y, T2 cannot begin

If T2 does not unlock X, T1 cannot continue

T1 & T2 wait indefinitely for each other to unlock data

n Deadlocks are only possible if a transactions wants an Exclusive Lock

(No Deadlocks on Shared Locks)

Controlling Deadlocks

n Prevention – A transaction requesting a new lock is aborted if there is the

possibility of a deadlock – Transaction is rolled back, Locks are released,

Transaction is rescheduled

n Detection – Periodically test the database for deadlocks. If a deadlock is found,

abort / rollback one of the transactions

n Avoidance – Requires a transaction to obtain all locks needed before it can

execute – requires locks to be obtained in succession

Time Stamping

n Creates a specific order in which the transactions are processed by the DBMS

n 2 Main Properties

!Uniqueness – Assumes that no equal time stamp value can exist (ensures serializability of the transactions)

!Monotonicity – Ensures that time stamp values always increases

n All operations within the same transaction have the same time stamp

n f Transactions conflict, one is rolled back and rescheduled

n Each value in Database requires 2 Additional Fields: Last Time Read / Last Time Updated

n Increases Memory Need and Processing Overhead

Time Stamping Schemes

n Wait / Die Scheme
The older transaction will wait

The younger transaction will be rolled back

n Wound / Wait Scheme

The older transaction will preempt (wound)

the younger transaction and roll it back

The younger transaction waits for the older

transaction to release the locks

n Without time-out values, Deadlocks may be created

Database Recovery

n Restore a database from a given state to a previous consistent state

n Atomic Transaction Property (All or None)

n Backup Levels:

n Full Backup

n Differential Backup

n Transaction Log Backup

n Database / System Failures:

n Software (O.S., DBMS, Application Programs, Viruses)

n Hardware (Memory Chips, Disk Crashes, Bad Sectors)

n Programming Exemption (Application Program rollbacks)

n Transaction (Aborting transactions due to deadlock detection)

n External (Fire, Flood, etc)

Transaction Recovery

n Recover Database by using data in the Transaction Log

n Write-Ahead-Log – Transaction logs need to be written before any database data is updated

n Redundant Transaction Logs – Several copies of log on different devices

n Database Buffers – Buffers are used to increase processing time on updates instead of accessing data on disk

n Database Checkpoints – Process of writing all updated buffers to disk à While this is taking place, all other requests are not executes

n Scheduled several times per hour

n Checkpoints are registered in the transaction log

analog communication

2012-05-17T11:26:00.000-07:00

A discrete signal or discrete-time signal is a function of a continuous argument; however, it may have been obtained by sampling from a continuous-time signal, and then each value in the sequence is called a sample.By acquiring values of an analog signal at constant or variable rate. This process is called sampling

time axis is discrete whereas in continuous single time axis is continuous .

A continuous signal or a continuous-time signal is a varying quantity (a signal) whose domain, which is often time, is a continuum (e.g., a connected interval of the reals). That is, the function's domain is an uncountable set. The function itself need not be continuous. To contrast, a discrete time signal has a countable domain, like the natural numbers.

A digital signal is discrete-time signal for which not only the time but also the amplitude has been made discrete; in other words, its samples take on only values from a discrete set

Digital signal

A deterministic signal is a signal in which each value of the signal is fixed and can be determined by a mathematical expression, rule, or table.

A non-deterministic signal has a lot of uncertainty about its behavior. The future values of a random signal cannot be accurately predicted and can usually only be guessed based on the averages of sets of signals For a non-deterministic signal the physical phenomenon cannot be represented mathematically.

Periodic signals repeat with some period T, while aperiodic, or nonperiodic, signals do not . We can define a periodic function through the following mathematical expression, where t can be any number and T is a positive constant:

f (t) = f (T + t)

(1)

The fundamental period of our function, f(t), is the smallest value of T that the still allows Equation 1 to be true.

(a) A periodic signal with period T0

ENERGY SIGNAL

If the total energy of a signal is a finite non-zero value, then that signal is classified as an energy signal.Typically the signals which are not periodic turns out to be energy signals. For example, a single rectangular pulse and a decaying exponential signal are energy signals.

POWER SIGNAL

If power of a signal is a finite non-zero value and its energy is infinite, then that signal is classified as a power signal.

The unit step

The unit step function is equal to zero when its index is negative and equal to one for non-negative indexes

UNIT STEP:

u(n)={1 if n≥00 otherwise

a signal that satisfies the unit step function is called unit step function.

Ramp signal

The Step signal can be interpreted as a ramp of width zero, when the ramp is defined as follows

Signum signal

The signum function of a real number x is defined as follows:

If the dependent variable x is replaced with the time the signal obtained is called signum signal.

Rectangular pulse

A rapid, transient change in the amplitude of a signal from a baseline value to a higher or lower value, followed by a rapid return to the baseline value is known as pulse and if pulse is in rectangular form it is called rectangular pulse signal.

The impulse signal

The impulse function, also known as Dirac delta function or Dirac impulse, is defined by

Linear system

A linear system is a mathematical model of a system based on the use of a linear operator. Linear systems typically exhibit features and properties that are much simpler than the general,nonlinear case. As a mathematical abstraction or idealization, linear systems find important applications in automatic control theory, signal processing, and telecommunications. For example, the propagation medium for wireless communication systems can often be modeled by linear systems.

A general deterministic system can be described by operator, , that maps an input, , as a function of to an output, , a type of black box description. Linear systems satisfy the properties of superposition and scaling or homogeneity. Given two valid inputs

as well as their respective outputs

then a linear system must satisfy

for any scalar values and .

Nonlinear system

nonlinear system is one that does not satisfy the superposition principle, or one whose output is not directly proportional to its input

Time-invariant system

A time-invariant (TIV) system is one whose output does not depend explicitly on time.

If the input signal produces an output then any time shifted input, , results in a time-shifted output

To demonstrate how to determine if a system is time-invariant then consider the two systems:

System A:

System B:

Since system A explicitly depends on t outside of and then it is not time-invariant. System B, however, does not depend explicitly on t so it is time-invariant.

Time-variant system

A time-variant system is a system that is not time invariant (TIV). Roughly speaking, characteristics of its output depend explicitly upon time.

for better understanding of time variant system . Let:

x(t) be an excitation signal.

T(x(t), t) be the describe the input–output map of a system in relaxed state.

y(t) be the system's output response to the excitation signal.

Stable and unstable systems

The stability of control systems is an important property. Considering any bounded input signal of a system, and if the output signal of the system to such a signal is also bounded, then the system is called bounded-input-bounded-output stable. If the output signal does not show this property, the system is unstable. For illustration see Figure .

Types of Transmission Media

Transmission Media

The means through which data is transformed from one place to another is called transmission or communication media. There are two categories of transmission media used in computer communications.

1.GUIDED MEDIA/BOUNDED MEDIA
2.UNGUIDED /UNBOUNDED MEDIA

Bounded media are the physical links through which signals are confined to narrow path. These are also called guide media. Bounded media are made up o a external conductor (Usually Copper) bounded by jacket material. Bounded media are great for LABS because they offer high speed, good security and low cast. However, some time they cannot be used due distance communication. Three common types of bounded media are used of the data transmission. These are

Coaxial Cable

Twisted Pairs Cable

Fiber Optics Cable

1.COAXIAL CABLE:

Coaxial cable is very common & widely used commutation media. For example TV wire is usually coaxial.

Coaxial cable gets its name because it contains two conductors that are parallel to each other. The center conductor in the cable is usually copper. The copper can be either a solid wire or stranded martial.

Outside this central Conductor is a non-conductive material. It is usually white, plastic material used to separate the inner Conductor form the outer Conductor. The other Conductor is a fine mesh made from Copper. It is used to help shield the cable form EMI.

ADVANTAGES COAXIAL CABLE

Inexpensive
Easy to wire
Easy to expand
Moderate level of EMI immunity

DISADVANTAGE COAXIAL CABLE

Single cable failure can take down an entire network
Twisted Pair Cable
The most popular network cabling is Twisted pair. It is light weight, easy to install, inexpensive and support many different types of network. It also supports the speed of 100 mps.Twisted pair cabling is made of pairs of solid or stranded copper twisted along each other. The twists are done to reduce vulnerably to EMI and cross talk. The number of pairs in the cable depends on the type. The copper core is usually 22-AWG or 24-AWG, as measured on the American wire gauge standard. There are two types of twisted pairs cabling

1. Unshielded twisted pair (UTP)

2. Shielded twisted pair (STP)

Unshielded twisted pair (UTP)

UTP is more common. It can be either voice grade or data grade depending on the condition. UTP cable normally has an impedance of 100 ohm. UTP cost less than STP and easily available due to its many use.
- - Characteristics of UTP
- low cost
- easy to install
- High speed capacity
- High attenuation
- Effective to EMI
- 100 meter limit
Advantages of UTP
- Easy installation
- Capable of high speed for LAN
- Low cost
Disadvantages of UTP
- Short distance due to attenuation
Shielded twisted pair (STP)

It is similar to UTP but has a mesh shielding that’s protects it from EMI which allows for higher transmission rate.

Characteristics of STP
Advantages of STP:
Disadvantages of STP:

Pipelining Processors

2012-05-14T07:08:00.000-07:00

Pipelining is a particularly effective way of organizing parallel activity in a computer system. The basic idea is very simple. It is frequently encountered in manufacturing plants, where pipelining is commonly known as an assembly line operation. By laying the production process out in an assembly line, product at various stages can be worked on simultaneously. This process is also referred to as pipelining, because, as in a pipeline, new inputs are accepted at one end before previously accepted inputs appear as outputs at the other end.

In simple words we can say

Pipelining is a technique of decomposing a sequential process into sub-operation with each sub-operation being executed in specially dedicated segments that operate concurrently with each other.

Instruction pipelininig

Let and refer to the fetch and execute steps for instruction . Execution of a program consists of a sequence of fetch and execute steps is shown in the Figure

Figure : Sequential Execution.

Now consider a CPU that has two separate hardware units, one for fetching instructions and another for executing them.

The instruction fetch by the fetch unit is stored in an intermediate storage buffer

The results of execution are stored in the destination location specified by the instruction.

For simplicity it is assumed that fetch and execute steps of any instruction can be completed in one clock cycle.

The operation of the computer proceeds as follows:

Both the fetch and execute units are kept busy all the time and one instruction is completed after each clock cycle except the first clock cycle. If a long sequence of instructions is executed, the completion rate of instruction execution will be twice that achievable by the sequential operation with only one unit that performs both fetch and execute.
Figure : Hardware Organization

1. In the first clock cycle, the fetch unit fetches an instruction (instruction , step  ) and stored it in buffer    at the end of the clock cycle.

2. In the second clock cycle, the instruction fetch unit proceeds with the fetch operation for instruction  (step  ).

3. Meanwhile, the execution unit performs the operation specified by instruction  which is already fetched and available in the buffer (step ).

4. By the end of the second clock cycle, the execution of the instruction is completed and instruction  is available.

5. instruction  is stored in buffer  replacing  , which is no longer needed.

6. Step  is performed by the execution unit during the third clock cycle, while instruction  is being fetched by the fetch unit.

7. Both the fetch and execute units are kept busy all the time and one instruction is completed after each clock cycle except the first clock cycle.

8. If a long sequence of instructions is executed, the completion rate of instruction execution will be twice that achievable by the sequential operation with only one unit that performs both fetch and execute.

Basic idea of instruction pipelining with hardware organization is shown in the Figure above

Figure : Pipeline Execution.

The processing of an instruction need not be divided into only two steps. To gain further speed up, the pipeline must have more stages.
Let us consider the following decomposition of the instruction execution:
- Fetch Instruction (FI): Read the next expected instruction into a buffer.
- Decode Instruction ((DI): Determine the opcode and the operand specifiers.
- Calculate Operand (CO): calculate the effective address of each source operand.
- Fetch Operands(FO): Fetch each operand from memory.
- Execute Instruction (EI): Perform the indicated operation.
- Write Operand(WO): Store the result in memory.
There will be six different stages for these six subtasks. For the sake of simplicity, let us assume the equal duration to perform all the subtasks. It the six stages are not of equal duration, there will be some waiting involved at various pipeline stages.
The timing diagram for the execution of instruction in pipeline fashion is shown in the Figure

Figure : Timing sequence in pipeline execution.

From this timing diagram it is clear that the total execution time of 8 instructions in this 6 stages pipeline is 13-time unit. The first instruction gets completed after 6 time unit, and there after in each time unit it completes one instruction.
Without pipeline, the total time required to complete 8 instructions would have been 48 (6 X 8) time unit. Therefore, there is a speed up in pipeline processing and the speed up is related to the number of stages.

Performance Issue

Now suppose that n instructions are processed and these instructions are executed one after another. The total time required to execute all n instructions is

The time required to execute n instructions without pipeline is Ti

speed up = Ti/Tk

Primary conflicts for instruction pipelining

1.Resource conflict: Caused by access to memory by two segments at the same time.

Most of these conflicts can be resolved by using seperate instruction and data memories

2.Data dependency: conflicts arise when an instruction depends on the result of a previous instruction but this result is not yet available.

3.Branch difficulties: arise from branch and other instructions that change the value of program counter

Resolution of conflicts

1.Hardware interlocks is method to remove data dependency conflict ,An interlock is a

circuit that detects instructions whose source operands are destinations of the instructions farther up in the pipeline.Detection of this situation causes the instruction whose source is not available to be delayed by enough clock cycles to resolve the conflict.

2.Operand forwarding another technique uses special hardware to detect a conflict and then avoid it by routing the data through special paths between pipeline segments.

for resolving the branch conflicts we first have to understand what a branch instruction is

A branch instruction is a instruction that alters the sequencial flow of the program by loading the program counter by targer address

3.Prefetch target instruction: In this technique pre-fetching of the target instruction is involve in addition to the instruction following the branch,both are saved until branch is executed if branching condition satisfied then pipeline continues from target instruction.
4.Branch target buffer: BTB is associative memory included in fetch segment .Each entry consists of address of previously executed branch instruction and target instruction . when pipeline decodes the branch instruction BTB search for the address of instruction if available then prefetch continues from new path.
5.Branch prediction: A pipeline with branch prediction uses special additional logic to predict the outcome of conditional branch and starts fetching the instruction stream from predicted path.
6.Delayed branch: In this procedure the compiler detects the branch and rearranges the machine code by adding some useful instruction that keep the pipeline operating without instrruptions.

Input output organization

2012-05-03T14:21:00.000-07:00

computer system's input output architecture is it's interface to the outside world.In most fundamental modules of computer ,I/O module have an important role besides the two PROCESSOR & MEMORY modules.Each I/O module interfaces to the system buses and control one or more peripheral devices .

Need for input output module

Intel 8085

2012-05-02T15:28:00.000-07:00

The Intel 8085 is an 8-bit microprocessor introduced by Intel in 1977 .The 8085 is a conventional Von Newman design based on Intel 8080 .It is having 8-bit data bus and 16-bit address but to limit the number of pins to 40.

instruction format continues

2012-05-02T03:40:00.000-07:00

just sit comfortably and enjoy addressing modes like eating popcorns

2012-05-01T21:46:00.000-07:00

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DATABASE MANAGEMENT SYSTEM

Concept of Normalization

Purpose of Normalisation Redundancy and Data Anomalies Functional Dependency Transitive Dependency Stages of Normalisation

Purpose of Normalisation

Redundancy and Data Anomalies

Functional Dependency

Normalization Achieves This!

Third normal form(3NF)

4th Normal Form

A Boyce Codd normal form relation is in fourth normal form if

What is a Transaction?

ACID Properties of a Transaction

Serializability

Locking

Time Stamping

Database Recovery

Transaction Recovery

analog communication

ENERGY SIGNAL

POWER SIGNAL

The unit step

Ramp signal

Signum signal

Rectangular pulse

The impulse signal

Linear system

Nonlinear system

Time-invariant system

Time-variant system

for better understanding of time variant system . Let:

Stable and unstable systems

Types of Transmission Media

Twisted Pair Cable

Characteristics of STP

Fiber Optics

Unbounded Transmission Media

Pipelining Processors

Primary conflicts for instruction pipelining

Resolution of conflicts

Input output organization

computer system's input output architecture is it's interface to the outside world.In most fundamental modules of computer ,I/O module have an important role besides the two PROCESSOR & MEMORY modules.Each I/O module interfaces to the system buses and control one or more peripheral devices .

Need for input output module

Intel 8085

The Intel 8085 is an 8-bit microprocessor introduced by Intel in 1977 .The 8085 is a conventional Von Newman design based on Intel 8080 .It is having 8-bit data bus and 16-bit address but to limit the number of pins to 40.

instruction format continues

just sit comfortably and enjoy addressing modes like eating popcorns

Purpose of Normalisation

Redundancy and Data Anomalies

Functional Dependency

Transitive Dependency

Stages of Normalisation