Pci Slots:Conventional PCI (part of the PCI Local Bus standard and often shortened to PCI) is a computer bus for attaching hardware devices in a computer. These devices can take either the form of an integrated circuit fitted onto the motherboard itself, called a planar device in the PCI specification, or an expansion card that fits into a slot. The name PCI is an initialism formed from Peripheral Component Interconnect. The PCI Local Bus is common in modern PCs, where it has displaced ISA and VESA Local Bus as the standard expansion bus, and it also appears in many other computer types. Despite the availability of faster interfaces such as PCI-X and PCI Express, conventional PCI remains a very common interface.

Typical PCI cards used in PCs include: network cards, sound cards, modems, extra ports such as USB or serial, TV tuner cards and disk controllers. Historically video cards were typically PCI devices, but growing bandwidth requirements soon outgrew the capabilities of PCI. PCI video cards remain available for supporting extra monitors and upgrading PCs that do not have any AGP or PCI Express slots.
When purchasing PCI expansion cards you need to be careful about compatibility with the PCI expansion slots on the motherboard. There are two things which vary in PCI expansion slots: the voltage, and the number of bits. PCI Slots can support either 3.3 volts or 5 volts. PCI has a system of keys which only allows expansion cards to fit into the motherboard connector if it provides the correct voltage. As shown in the picture above, a 5 volt PCI motherboard connector has a key near the right end. A 5 volt PCI expansion card has a slot which lines up with the key. That allows you to plug a 5 volt PCI card into a 5 volt PCI connector. You can see a "real" PCI connector in the motherboard picture above. 3.3 volts is similar but its key is near the left end. This system allows you to plug 5 volt cards into 5 volt PCI connectors but not into 3.3 volt PCI connectors. Likewise, you can only plug 3.3 volt cards into 3.3 volt PCI connectors and not into 5 volt connectors. If the expansion card can run on both 3.3 and 5 volts then it has both slots and fits into both 3.3 and 5 volt PCI motherboard connectors. PCI expansion slots also support two different widths: 32 bits, and 64 bits. The 64 bit motherboard connector is longer than a 32 bit connector. Most PC motherboards come with 32 bit slots but some come with 64 bit slots. A 32 bit PCI expansion card will work fine in a 64 bit slot. PCI video cards are 32 bit cards. 

BIOS(Basic input output sysytem):The BIOS is boot firmware, designed to be the first code run by a PC when powered on. The initial function of the BIOS is to identify, test, and initialize system devices such as the video display card, hard disk, floppy disk and other hardware. The BIOS prepares the machine for a known state, so that software stored on compatible media can be loaded, executed, and given control of the PC. This process is known as booting, or booting up, which is short for bootstrapping.
BIOS programs are stored on a chip(ROM) and are built to work with various devices that make up the complementary chipset of the system.

CMOS(Complementary metal–oxide–semiconductor):As described above in your computer is a chip called the BIOS chip. This chip contains all of the basic instructions that tell your motherboard how to operate. However, every motherboard has several settings that can be changed by the user, including the date and time, the types of drives installed in the computer, the system bus speed and more. These settings cannot be saved to the BIOS, because the BIOS exists on a type of memory that cannot be written to called ROM. To retain your settings, the motherboard also has a second type of memory called the CMOS. CMOS memory can be written to, but it also requires a very small electrical current in order to retain this information. Therefore, the CMOS is powered by a battery. Because of the CMOS battery, all of your settings are saved even when the computer is turned off or disconnected from a power source.
note:"CMOS is a type of battery often used to power the circuit which allows the information in BIOS to be stored. If the CMOS battery is drained or removed all the system configuration data in BIOS will be reset to factory defaults every time the computer is shut off."



AGPslot:The Accelerated Graphics Port (also called Advanced Graphics Port, often shortened to AGP) is a high-speed point-to-point channel for attaching a video card to a computer's motherboard, primarily to assist in the acceleration of 3D computer graphics.
 As computers became increasingly graphically oriented, successive generations of graphics adapters began to push the limits of PCI, a bus with shared bandwidth. This led to the development of AGP, a "bus" dedicated to graphics adapters.
The primary advantage of AGP over PCI is that it provides a dedicated pathway between the slot and the processor rather than sharing the PCI bus. In addition to a lack of contention for the bus, the point-to-point connection allows for higher clock speeds.





South Bridge:The south bridge incorporates a number of different controller functions. It looks after the transfer of data to and from the hard disk and all the other I/O devices, and passes this data into the link channel which connects to the north bridge. 

The images you see on your monitor are made of tiny dots called pixels. At most common resolution settings, a screen displays over a million pixels, and the computer has to decide what to do with every one in order to create an image. To do this, it needs a translator -- something to take binary data from the CPU and turn it into a picture you can see. Unless a computer has graphics capability built into the motherboard, that translation takes place on the graphics card.
A graphics card's job is complex, but its principles and components are easy to understand. In this article, we will look at the basic parts of a video card and what they do. We'll also examine the factors that work together to make a fast, efficient graphics card.

­ Think of a computer as a company with its own art department. When people in the company want a piece of artwork, they send a request to the art department. The art department decides how to create the image and then puts it on paper. The end result is that someone's idea becomes an actual, viewable picture.
A graphics card works along the same principles. The CPU, working in conjunction with software applications, sends information about the image to the graphics card. The graphics card decides how to use the pixels on the screen to create the image. It then sends that information to the monitor through a cable. ­
Creating an image out of binary data is a demanding process. To make a 3-D image, the graphics card first creates a wire frame out of straight lines. Then, it rasterizes the image (fills in the remaining pixels). It also adds lighting, texture and color. For fast-paced games, the computer has to go through this process about sixty times per second. Without a graphics card to perform the necessary calculations, the workload would be too much for the computer to handle.
The graphics card accomplishes this task using four main components:

• A motherboard connection for data and power
• A processor to decide what to do with each pixel on the screen
• Memory to hold information about each pixel and to temporarily store completed pictures
• A monitor connection so you can see the final result

Next, we'll look at the processor and memory in more detail.
Like a motherboard, a graphics card is a printed circuit board that houses a processor and RAM. It also has an input/output system (BIOS) chip, which stores the card's settings and performs diagnostics on the memory, input and output at startup. A graphics card's processor, called a graphics processing unit (GPU), is similar to a computer's CPU. A GPU, however, is designed specifically for performing the complex mathematical and geometric calculations that are necessary for graphics rendering. Some of the fastest GPUs have more transistors than the average CPU. A GPU produces a lot of heat, so it is usually located under a heat sink or a fan.
In addition to its processing power, a GPU uses special programming to help it analyze and use data. ATI and nVidia produce the vast majority of GPUs on the market, and both companies have developed their own enhancements for GPU performance. To improve image quality, the processors use:

• Full scene anti aliasing (FSAA), which smoothes the edges of 3-D objects
• Anisotropic filtering (AF), which makes images look crisper

­ Each company has also developed specific techniques to help the GPU apply colors, shading, textures and patterns.

­ As the GPU creates images, it needs somewhere to hold information and completed pictures. It uses the card's RAM for this purpose, storing data about each pixel, its color and its location on the screen. Part of the RAM can also act as a frame buffer, meaning that it holds completed images until it is time to display them. Typically, video RAM operates at very high speeds and is dual ported, meaning that the system can read from it and write to it at the same time.
­ The RAM connects directly to the digital-to-analog converter, called the DAC. This converter, also called the RAMDAC, translates the image into an analog signal that the monitor can use. Some cards have multiple RAMDACs, which can improve performance and support more than one monitor. You can learn more about this process in How Analog and Digital Recording Works.
The RAMDAC sends the final picture to the monitor through a cable. We'll look at this connection and other interfaces in the next section.



­Graphics cards connect to the computer through the motherboard. The motherboard supplies power to the card and lets it communicate with the CPU. Newer graphics cards often require more power than the motherboard can provide, so they also have a direct connection to the computer's power supply.
Connections to the motherboard are usually through one of three interfaces:

• Peripheral component interconnect (PCI)
• Advanced graphics port (AGP)
• PCI Express (PCIe)

PCI Express is the newest of the three and provides the fastest transfer rates between the graphics card and the motherboard. PCIe also supports the use of two graphics cards in the same computer.­Most graphics cards have two monitor connections. Often, one is a DVI connector, which supports LCD screens, and the other is a VGA connector, which supports CRT(cathode ray tube) screens. Some graphics cards have two DVI connectors instead. But that doesn't rule out using a CRT screen; CRT screens can connect to DVI ports through an adapter. At one time, Apple made monitors that used the proprietary Apple Display Connector (ADC). Although these monitors are still in use, new Apple monitors use a DVI connection.
Most people use only one of their two monitor connections. People who need to use two monitors can purchase a graphics card with dual head capability, which splits the display between the two screens. A computer with two dual head, PCIe-enabled video cards could theoretically support four monitors.
In addition to connections for the motherboard and monitor, some graphics cards have connections for:

• TV display: TV-out or S-video
• Analog video cameras: ViVo or video in/video out
• Digital cameras: FireWire or USB

Some cards also incorporate TV tuners. Next, we'll look at how to choose a good graphics card.


A top-of-the-line graphics card is easy to spot. It has lots of memory and a fast processor. Often, it's also more visually appealing than anything else that's intended to go inside a computer's case. Lots of high-performance video cards are illustrated or have decorative fans or heat sinks.
But a high-end card provides more power than most people really need. People who use their computers primarily for e-mail, word processing or Web surfing can find all the necessary graphics support on a motherboard with integrated graphics. A mid-range card is sufficient for most casual gamers. People who need the power of a high-end card include gaming enthusiasts and people who do lots of 3-D graphic work.

Some cards, like the ATI All-in-Wonder, include connections for televisions and video as well as a TV tuner.

A good overall measurement of a card's performance is its frame rate, measured in frames per second (FPS). The frame rate describes how many complete images the card can display per second. The human eye can process about 25 frames every second, but fast-action games require a frame rate of at least 60 FPS to provide smooth animation and scrolling. Components of the frame rate are:

• Triangles or vertices per second: 3-D images are made of triangles, or polygons. This measurement describes how quickly the GPU can calculate the whole polygon or the vertices that define it. In general, it describes how quickly the card builds a wire frame image.
• Pixel fill rate: This measurement describes how many pixels the GPU can process in a second, which translates to how quickly it can rasterize the image.

The graphics card's hardware directly affects its speed. These are the hardware specifications that most affect the card's speed and the units in which they are measured:

• GPU clock speed (MHz)
• Size of the memory bus (bits)
• Amount of available memory (MB)
• Memory clock rate (MHz)
• Memory bandwidth (GB/s)
• RAMDAC speed (MHz)

­ The computer's CPU and motherboard also play a part, since a very fast graphics card can't compensate for a motherboard's inability to deliver data quickly. Similarly, the card's connection to the motherboard and the speed at which it can get instructions from the CPU affect its performance.

Many motherboards have integrated graphics capabilities and function without a separate graphics card. These motherboards handle 2-D images easily, so they are ideal for productivity and Internet applications. Plugging a separate graphics card into one of these motherboards overrides the onboard graphics functions.

BOOTING UP

It is useful to understand what happens behind the scenes when you switch on your computer from a cold idle machine to an operable and functional system. There are essentially two forms of booting - the soft boot and the hard boot.
The cold boot or hard boot involves powering the computer up from an initial zero power supply.
A warm boot on the other hand takes place when a software application or operating system triggers the computer to perform a reboot.
A successful boot is dependent on 3 conditions - the hardware, BIOS and operating system files to function without errors. When an error occurs, you will be notified by error messages, beeping sounds or in the worst scenario, a blank screen.

BOOTUP PROCESS

The bootup process is a list of detailed procedures that the system undergoes to perform all system checks and load all necessary files to bring the computer to an operable state.

The Windows XP bootup process comprises of the following procedures:

A.THE POWER-ON SELF TEST PHASE

As soon as you power up your computer, a self-test is performed by the power supply to ensure that the volume and current levels are correct before the Power Good signal is sent to the processor. When this first stage is cleared, the microprocessor will then trigger the BIOS to perform a series of operations.
 

B. BIOS ROM PHASE

The BIOS, also known as the Basic Input Output System is a firmware or set of instructions that resides on a ROM chip as contained in the motherboard.
It first carries out the P.O.S.T that performs and verifies all initial hardware checks, such as checking if the system is initialized by a warm or cold start, detecting the presence of peripheral devices and the amount of memory present.
It then accesses the information stored in the CMOS chip, DIP switches, jumpers and assigns the necessary system resources. After this, the hardware' firmware will individually carry out its own diagnostic test such as S.M.A.R.T.
The system will now attempt to determine the sequence of devices to load based on the settings stored in the BIOS to start the operating system. It will start by reading from the first bootup device. If it points to the floppy drive, it then searches for a floppy disk. If it does not detect a bootable diskette in the floppy drive, the system displays an error message.
If the floppy drive does not contain a diskette, it bypasses the first bootup device and detects the second device, which is usually the hard disk. It'll then start by reading the boot code instructions located in the master boot record and copies all execution into the memory when the instructions are validated and no errors are found.

C. BOOT LOADER PHASE

Control is then passed on to the partition loader code which accesses the partition table to identify the primary partition, extended partitions and active partition which is needed to determine the file system and locate the operating system loader file - NTLDR. NTLDR will then switch the processor from real-mode to 32 bit protected mode which memory paging is enabled.
NTLDR will call upon the boot.ini file which is located at the root directory to determine the location and entries of the operating system boot partition. At this point in time, the bootup menu is displayed on the screen to allow you to select an operating system to start from if you have more than 2 operating systems installed in your computer.
NTLDR will pass all information from the Windows registry and Boot.ini file into Ntoskrnl.exe.

D. OPERATING SYSTEM CONFIGURATION PHASE

Ntoskrnl will begin to load the XP kernel, hardware abstraction layer and registry information. After this is completed, the control is passed over to the DOS based Ntdetect.com program which collects and configures all installed hardware devices such as the video adapters and communication ports.
Ntdetect.com then searches for hardware profiles information and load the essential software drivers to control the hardware devices.

E. SECURITY & LOGON PHASE

Lastly, Ntoskrnl.exe will start up Winlogon.exe which triggers the Lsass.exe or Local Security Administration which is the logon dialog interface that prompts you to select your user profile and verifies your necessary credentials before you are transferred to the Windows desktop.

Friendship Quotes

Birthday Quotes

Funny Quotes

Before the clock strikes twelve let me take the opportunity to let you know that you have grown a year more...
Happy birthday...

This msg has No Fat
No cholesterol n No Addictive
this is all natural except, with a lot of sugar. But it can never be as sweet as the one reading it.Happy Birthday

Kick off ur shoes, take a break, Crank the tunes, Dance & Shake, light the candles, cut the cake. Make it a day, that's simply Great!!! Happy B'Day..

Smile is a curve that sets everything straight and wipes wrinkle away
hope u share a lots and receive a lots 4 days 2 come
happy Birthday .......

I know its your birthday today.. I am sure u will give me treat in a big hotel.. so I shall talk to you in person there, because I don't know to express my feelings in SMS.

Apun wishing you a wonderful, super duper, zabardast, extra bariya, extra special ekdum mast n dhinchak bole to ekdum jhakaas, JANAM DIN mubarak ho..

Nobody teaches
Volcanoes to erupt,
Tsunamis to devastate,
Hurricanes to sway around
&
no one teaches
How to choose a Wife,

NATURAL DISASTERS JUST HAPPEN.

Most interesting line written
on the front of T-shirt of a girl,
.
.
.
.
.
.
.
Excuse me !
My face is above.;-)

Husband wanted to call the hospital
to ask about his pregnant wife,
but accidently called the cricket stadium.

He asks, “How’s the situation?”

He was shocked & nearly died on hearing the reply.

They said, “It’s fine. 3 are out,
hope to get another 7 out by lunch,
last one was a duck!”..:-P

READ THIS SCARY STORY IF YOU DARE.
On a rainy day,
an old man was standing with a book for sale.
A young man came to buy.
He bought the book for Rs.3000.
Old man advised
“DONT OPEN LAST PAGE OF THE BOOK othrwise YOU’ll face problem”
Man finished the book with great fear but didnt open the last page.
.
.
.
But,after a week,
Out of curiousity he opend the last page and..

he almost fainted to see..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Retail Price: Rs 30/-

In a practical Exam
Examiner showed legs of bird n said:Tell the bird’s name
Sardar:I dont know
Exminer: U r failed.Wats ur name?
Sardar: You see my legs, and tell me.

A sardar ji pulled out 6 people from a burning house…
still he was in jail…….why?
coz all the 6 were fire brigade staff !

Sometimes wen i cry no 1 c my tears,
wen i m woried no 1 c my pain,
wen i m happy no 1 c my smile
lekin…
sala. 1 ladki k saath ghoomay
to sab dekh lete hai..

Importance of thumb…

Children use it 4 chewing

Illiterate people use it 4 sign

Winners 4 victory
.
.
AND
.
.
My FANS use it 4 reading my messages
.
.
.
.
.
Oh….u toooo?

Taste this SMS
Did u feel da taste of ginger?
No?
Sure?
Well…..
BANDAR KYA JAANE ADRAK KA SWAAD!!

A person who surrenders when he’s WRONG,
is HONEST.
A person who SURRENDERS when not SURE,
is WISE.
A person who surrenders even if he’s RIGHT,
is a HUSBAND.!

A recently fired
stock trader said …

“This is worse than divorce…
I have lost everything
and
I still have my wife…

Teacher : What do you call a person
who keeps on talking when
people are no longer interested?

Pupil : A teacher.

A : u r Active
B : u r Best
C : u r Cute
D : u r my Dearest
E : u r Excelant
F : u r alwayz First
G : u r Great
Sorry cant lie till Z…

Two devils came in 2 my dreams.
They said,
“We want 2 disturb some good person.”
I suggest them your name.
They said,
“We cannot disturb our boss.

Teacher : Correct the sentence,
“A bull and a cow is grazing in the field”

Student : “A cow and a bull is grazing in the field”
Teacher : How?

Student : Ladies first.

Before Marriage:-

He: yes! atlast it was so hard 2 wait
she:do you want me 2 leave?
He: No! don’t even think about it
She: do you love me ?
He:ofcourse! over n over!
She:have u ever cheated on me?
He:No!y r u even asking?
She:will u go on wid me on picnic?
He:every chance I get!
She:will u hit me ?
He:R u crazy?I’m not that kind of person!
She:can I trust u?
He:yes..
She: Darling!

After marriage…
Now simply read from bottom to top

When u feel sad….
To cheer up just go to the mirror and say,
“damn I am really so cute”
u will overcome your sadness.
But don’t make this a habit…..
Coz liars go to hell !!!!

Man : How old is your father?
Boy : As old as me.
Man : How can that be?
Boy : He became a father only when I was born

Do u know whats A B C D E F G?
A Boy Can Do Everything For Girl

Now reverse da order, can u guess the full form of: G F E D C B A ?
Girls Forgets Everything Done & Catches(new) Boy Again.

Girl:It’s 2 tight
Boy:Don’t worry,I’ll do it slowly,
Gal:Push it in,
Boy:Ah..I can’t,
Gal:It’s painful,
Boy:Forget it.
.
.
.
.
We’ll buy new WEDDING RING!

Never KISS a lady police,
She will say, hands up.

Never KISS a lady doctor,
She will say, Next please

Always KISS a lady teacher,
She will say, repeat it 5 time

A beautiful girl goes to Professor cabin
and
say
that i will do anything to pass in the exams
and professor says
NOW OPEN YOUR
.
.
.
.
.
.
Books And Study

if sumone calls u crazy,dont mind,
if sumone calls u duffer,relax,
if sumone calls u stupid be cool,
but if sumone calls u “cute”
.
.
.
.
lagana thappar os pagal ke monh pe,
mazak ki b koi hud hoti hai

Catch her by her waist…
Bring her home..
Keep ur hand on her neck
Put ur lips on her lips
& have a …
…nice drink…PEPSI

Friendship is not about finding similarities, it is about respecting differences. You are not my friend coz you are like me, but because i accept you and respect you the way you are.

Thank you for touching my life in ways you may never know. My riches do not lie in material wealth, but in having friend like you - a precious gift from God.

Good FRIENDS CaRE for each Other..
CLoSE Friends UNDERSTaND each Other...
and TRUE Friends STaY forever
beyond words,
beyond time.

FRiEND in different lanaguages...
Iranian - DOST
German - FREUND
Herbew - CHAVER
French - AMi
Pinoy - KAiBiGAN
Dutch - VREND
Mexican - AMiGO

For me.. just simply "YOU"

In this cruel world it is very difficult to find friend with beautiful heart, pure feelings, attractive personality & stylish looks. So learn to value me!

When I was born, GOD said, "Oh No! Another IDIOT". When you were born, GOD said, "OH No! COMPETITION". Who knew, one day these two will become FREINDS FOREVER!

When does a friend become a best friend?
When his dialouge, "I care for you" converts into "I will kill you if you don't care for me"

Science has proved that sugar melts in water,so plz don`t walk in the rain,
otherwise I may lose a sweet friend like u!!!

Friendship is not a big fire which burns all day. Its a small lamp, that burns till the last day of life

Medicines and friendships cure our problems. The only difference is that friendships don't have an expiry date.

Microprocessor Progression: Intel

The Intel 8080 was the first microprocessor in a home computer.

Name	Date	Transistors	Microns	Clock speed	Data width	MIPS
8080	1974	6,000	6	2 MHz	8 bits	0.64
8088	1979	29,000	3	5 MHz	16 bits 8-bit bus	0.33
80286	1982	134,000	1.5	6 MHz	16 bits	1
80386	1985	275,000	1.5	16 MHz	32 bits	5
80486	1989	1,200,000	1	25 MHz	32 bits	20
Pentium	1993	3,100,000	0.8	60 MHz	32 bits 64-bit bus	100
Pentium II	1997	7,500,000	0.35	233 MHz	32 bits 64-bit bus	~300
Pentium III	1999	9,500,000	0.25	450 MHz	32 bits 64-bit bus	~510
Pentium 4	2000	42,000,000	0.18	1.5 GHz	32 bits 64-bit bus	~1,700
Pentium 4 "Prescott"	2004	125,000,000	0.09	3.6 GHz	32 bits 64-bit bus	~7,000

Information about this table:

• The date is the year that the processor was first introduced. Many processors are re-introduced at higher clock speeds for many years after the original release date.
• Transistors is the number of transistors on the chip. You can see that the number of transistors on a single chip has risen steadily over the years.
• Microns is the width, in microns, of the smallest wire on the chip. For comparison, a human hair is 100 microns thick. As the feature size on the chip goes down, the number of transistors rises.
• Clock speed is the maximum rate that the chip can be clocked at. Clock speed will make more sense in the next section.
• Data Width is the width of the ALU. An 8-bit ALU can add/subtract/multiply/etc. two 8-bit numbers, while a 32-bit ALU can manipulate 32-bit numbers. An 8-bit ALU would have to execute four instructions to add two 32-bit numbers, while a 32-bit ALU can do it in one instruction. In many cases, the external data bus is the same width as the ALU, but not always. The 8088 had a 16-bit ALU and an 8-bit bus, while the modern Pentiums fetch data 64 bits at a time for their 32-bit ALUs.
• MIPS stands for "millions of instructions per second" and is a rough measure of the performance of a CPU. Modern CPUs can do so many different things that MIPS ratings lose a lot of their meaning, but you can get a general sense of the relative power of the CPUs from this column.

Microprocessor Logic

IntelPentium 4 processor

• Using its ALU (Arithmetic/Logic Unit), a microprocessor can perform mathematical operations like addition, subtraction, multiplication and division. Modern microprocessors contain complete floating point processors that can perform extremely sophisticated operations on large floating point numbers.
• A microprocessor can move data from one memory location to another.
• A microprocessor can make decisions and jump to a new set of instructions based on those decisions.

• An address bus (that may be 8, 16 or 32 bits wide) that sends an address to memory
• A data bus (that may be 8, 16 or 32 bits wide) that can send data to memory or receive data from memory
• An RD (read) and WR (write) line to tell the memory whether it wants to set or get the addressed location
• A clock line that lets a clock pulse sequence the processor
• A reset line that resets the program counter to zero (or whatever) and restarts execution

• Registers A, B and C are simply latches made out of flip-flops.
  
• The address latch is just like registers A, B and C.
• The program counter is a latch with the extra ability to increment by 1 when told to do so, and also to reset to zero when told to do so.
• The ALU could be as simple as an 8-bit adder,or it might be able to add, subtract, multiply and divide 8-bit values. Let's assume the latter here.
• The test register is a special latch that can hold values from comparisons performed in the ALU. An ALU can normally compare two numbers and determine if they are equal, if one is greater than the other, etc. The test register can also normally hold a carry bit from the last stage of the adder. It stores these values in flip-flops and then the instruction decoder can use the values to make decisions.
• There are six boxes marked "3-State" in the diagram. These are tri-state buffers. A tri-state buffer can pass a 1, a 0 or it can essentially disconnect its output (imagine a switch that totally disconnects the output line from the wire that the output is heading toward). A tri-state buffer allows multiple outputs to connect to a wire, but only one of them to actually drive a 1 or a 0 onto the line.
• The instruction register and instruction decoder are responsible for controlling all of the other components.

• Tell the A register to latch the value currently on the data bus
• Tell the B register to latch the value currently on the data bus
• Tell the C register to latch the value currently output by the ALU
• Tell the program counter register to latch the value currently on the data bus
• Tell the address register to latch the value currently on the data bus
• Tell the instruction register to latch the value currently on the data bus
• Tell the program counter to increment
• Tell the program counter to reset to zero
• Activate any of the six tri-state buffers (six separate lines)
• Tell the ALU what operation to perform
• Tell the test register to latch the ALU's test bits
• Activate the RD line
• Activate the WR line

Microprocessor Memory

ROM chip

RAM chip

Microprocessor Instructions

• LOADA mem - Load register A from memory address
• LOADB mem - Load register B from memory address
• CONB con - Load a constant value into register B
• SAVEB mem - Save register B to memory address
• SAVEC mem - Save register C to memory address
• ADD - Add A and B and store the result in C
• SUB - Subtract A and B and store the result in C
• MUL - Multiply A and B and store the result in C
• DIV - Divide A and B and store the result in C
• COM - Compare A and B and store the result in test
• JUMP addr - Jump to an address
• JEQ addr - Jump, if equal, to address
• JNEQ addr - Jump, if not equal, to address
• JG addr - Jump, if greater than, to address
• JGE addr - Jump, if greater than or equal, to address
• JL addr - Jump, if less than, to address
• JLE addr - Jump, if less than or equal, to address
• STOP - Stop execution

a=1;
f=1;
while (a <= 5)
{
    f = f * a;
    a = a + 1;
}

// Assume a is at address 128
// Assume F is at address 129
0   CONB 1      // a=1;
1   SAVEB 128
2   CONB 1      // f=1;
3   SAVEB 129
4   LOADA 128   // if a > 5 the jump to 17
5   CONB 5
6   COM
7   JG 17
8   LOADA 129   // f=f*a;
9   LOADB 128
10  MUL
11  SAVEC 129
12  LOADA 128   // a=a+1;
13  CONB 1
14  ADD
15  SAVEC 128
16  JUMP 4       // loop back to if
17  STOP

ROM

• LOADA - 1
• LOADB - 2
• CONB - 3
• SAVEB - 4
• SAVEC mem - 5
• ADD - 6
• SUB - 7
• MUL - 8
• DIV - 9
• COM - 10
• JUMP addr - 11
• JEQ addr - 12
• JNEQ addr - 13
• JG addr - 14
• JGE addr - 15
• JL addr - 16
• JLE addr - 17
• STOP - 18

// Assume a is at address 128
// Assume F is at address 129
Addr opcode/value
0    3             // CONB 1
1    1
2    4             // SAVEB 128
3    128
4    3             // CONB 1
5    1
6    4             // SAVEB 129
7    129
8    1             // LOADA 128
9    128
10   3             // CONB 5
11   5
12   10            // COM
13   14            // JG 17
14   31
15   1             // LOADA 129
16   129
17   2             // LOADB 128
18   128
19   8             // MUL
20   5             // SAVEC 129
21   129
22   1             // LOADA 128
23   128
24   3             // CONB 1
25   1
26   6             // ADD
27   5             // SAVEC 128
28   128
29   11            // JUMP 4
30   8
31   18            // STOP

Decoding

1. During the first clock cycle, we need to actually load the instruction. Therefore the instruction decoder needs to:
   
   
   
   • activate the tri-state buffer for the program counter
   • activate the RD line
   • activate the data-in tri-state buffer
   • latch the instruction into the instruction register
   
   
   
   
2. During the second clock cycle, the ADD instruction is decoded. It needs to do very little:
   
   
   
   • set the operation of the ALU to addition
   • latch the output of the ALU into the C register
   
   
   
   
3. During the third clock cycle, the program counter is incremented (in theory this could be overlapped into the second clock cycle).

Microprocessor Performance and Trends

64-bit Microprocessors

Photo courtesy AMD