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The Arithmetic Logic Unit Information Technology Essay

Paper Type: Free Essay Subject: Information Technology
Wordcount: 3992 words Published: 1st Jan 2015

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Computer memory is one of the technologies that are used to store information in electronic device. Compare the various types of memory in terms of capacity, performance, access methods, physical types, and characteristics.

Year by year, the cost of computer systems continues to drop dramatically while the performance and capacity of the systems continue to rise equally dramatically. Find out and write about the evolution of microprocessor system. Give an example to support your answer.

The microprocessor incorporates most of the all of the functions of the computer’s central processing unit (CPU) on the single integrated circuit (IC, or microchip).

First microprocessors emerged in the early 1970s and were used for electronic calculators, using binary-coded decimal (BCD) arithmetic on 4-bit words. Other embedded uses of 4-bit and 8-bit microprocessors, such as terminals, printers, various kinds of automation etc., followed soon after. Affordable 8-bit microprocessors with 16-bit addressing also led to the first general-purpose microcomputers from the mid-1970s on.

Microprocessor Components

Some of the common components of the microprocessor are:

Control Unit

I/O Units

Arithmetic Logic Unit (ALU)

We will give the brief introduction to these components below.

Control Unit

The control unit, has been described above, reads the instructions, and generates the necessary digital signals to operate the other components. An instruction to add two numbers together would cause the Control Unit to activate the addition module, for instance.

I/O Units

The processor needs to be able to communicate with the rest of the computer system. This communications occur through the I/O port. The I/O ports will interface with the system memory (RAM), and also the other peripherals of a computer.

Arithmetic Logic Unit

The Arithmetic Logic Unit or ALU is the part of the microprocessor that performs arithmetic operations. ALUs can typically add, subtract, divide, multiply, and perform logical operations of two numbers (and, or, nor, not, etc).

That the silicon chips that contains the CPU. In the world of the personal computers, the terms microprocessor and CPU are used interchangeably. At the heart of all personal computers and most workstations sits a microprocessor. Microprocessors also control the logic of almost all digital devices, from clock radios to fuel-injection systems for automobiles.

Three basic characteristics differentiate microprocessors:

Instruction set: The set of instructions that the microprocessor can execute.

Bandwidth : The number of bits processed in a single instruction.

Clock speed : Given in megahertz (MHz), the clock speed determines how many instructions per second the processor can execute.

In the both cases, the higher the value, the more powerful is the CPU. For example, a 32-bit microprocessor that runs at 50MHz is more powerful than a 16-bit microprocessor that runs at 25MHz.

In addition to bandwidth and clock speed, microprocessors are classified as being either RISC (reduced instruction set computer) or CISC (complex instruction set computer).

Types of Microprocessors

There are different ways in which the microprocessors are categorized.

They are

CISC (Complex Instruction Set Computers)

RISC(Reduced Instruction Set Computers)

VLIW(Very Long Instruction Word Computers)

Super scalar processors

Other types of specialized processors are

General Purpose Processor (GPP)

Special Purpose Processor (SPP)

Application-Specific Integrated Circuit (ASIC)

Digital Signal Processor (DSP)

Working of a Microprocessor

it’s the central processing unit which that coordinates all the functions of the computer. It generates timing signals, sends and receives data to and from every peripheral used inside or outside the computer. The commands required to do this are fed into the device in the form of current variations which are converted into meaningful instructions by the use of the Boolean Logic System. It divides its functions in two categories, logical functions and processing functions. The arithmetic and logical unit and the control unit handle these functions respectively. The information is communicated through the bunch of wires called buses. The address bus carries the ‘address’ of the location with which communication is desired while the data bus carries the data that is being exchanged.

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The microprocessor is that of the single chip integrating all the functions of the central processing unit (CPU) of the computer. It includes all the logical functions, data storage, timing functions and interaction with other peripheral devices. In some cases, the terms ‘CPU’ and ‘microprocessor’ are used interchangeably to denote the same device. Like every genuine engineering marvel, the microprocessor too has evolved through the series of improvements throughout the 20th century..

This invention of the transistor in 1947 was the significant development in the world of technology. It could perform the function of a large component used in a computer in the early years. Shockley, Brattain and Bardeen are credited with this invention and were awarded the Nobel Prize for the same. Soon it was found that the function this large component was easily performed by a group of transistors arranged on a single platform. This platform, known as the integrated chip (IC), turned out to be a very crucial achievement and brought along a revolution in the use of computers. A person named Jack Kilby of Texas Instruments was honored with the Nobel Prize for the invention of IC, which laid the foundation on which microprocessors were developed. At the same time, Robert Noyce of Fairchild made a parallel development in IC technology for which he was awarded the patent.

ICs proved beyond doubt that complex functions could be integrated on a single chip with a highly developed speed and storage capacity. Both Fairchild and Texas Instruments began the manufacture of commercial ICs in 1961. Later, complex developments in the IC led to the addition of more complex functions on a single chip. The stage was set for a single controlling circuit for all the computer functions. Finally, Intel Corporation’s Ted Hoff and Frederico Fagin were credited with the design of the first microprocessor.

The work on this project began with an order from a Japanese calculator company Busicom to Intel, for building some chips for it. Hoff felt that the design could integrate a number of functions on a single chip making it feasible for providing the required functionality. This led to the design of Intel 4004, the world’s first microprocessor. The next in line was the 8 bit 8008 microprocessor. It was developed by Intel in 1972 to perform complex functions in harmony with the 4004.

This was the beginning of a new era in computer applications. The use of mainframes and huge computers was scaled down to a much smaller device that was affordable to many. Earlier, their use was limited to large organizations and universities. With the advent of microprocessors, the use of computers trickled down to the common man. The next processor in line was Intel’s 8080 with an 8 bit data bus and a 16 bit address bus. This was amongst the most popular microprocessors of all time.

Very soon, the Motorola Corporation developed its own 6800 in competition with the Intel’s 8080. Fagin left Intel and formed his own firm Zilog. It launched a new microprocessor Z80 in 1980 that was far superior to the previous two versions. Similarly, a break off from Motorola prompted the design of 6502, a derivative of the 6800. Such attempts continued with some modifications in the base structure.

The use of microprocessors was limited to task-based operations specifically required for company projects such as the automobile sector. The concept of a ‘personal computer’ was still a distant dream for the world and microprocessors were yet to come into personal use. The 16 bit microprocessors started becoming a commercial sell-out in the 1980s with the first popular one being the TMS9900 of Texas Instruments.

Intel developed the 8086 which still serves as the base model for all latest advancements in the microprocessor family. It was largely a complete processor integrating all the required features in it. 68000 by Motorola was one of the first microprocessors to develop the concept of microcoding in its instruction set. They were further developed to 32 bit architectures. Similarly, many players like Zilog, IBM and Apple were successful in getting their own products in the market. However, Intel had a commanding position in the market right through the microprocessor era.

The 1990s saw a large scale application of microprocessors in the personal computer applications developed by the newly formed Apple, IBM and Microsoft corporation. It witnessed a revolution in the use of computers, which by then was a household entity.

Computer memory is one of the technologies that are used to store information in electronic device. Compare the various types of memory in terms of capacity, performance, access methods, physical types, and characteristics.

Types of the RAM

Top L-R, DDR2 with heat-spreader, and DDR2 without heat-spreader, Laptop DDR2, DDR, Laptop DDR

1 Megabit chip – is one of the last models developed by VEB Carl Zeiss Jena in 1989

Modern types of writable RAM generally store a bit of data in either the state of a flip-flop, as in SRAM (static RAM), or as a charge in a capacitor (or transistor gate), as in DRAM(dynamic RAM), EPROM, EEPROM and Flash. Some types have circuitry to detect and/or correct random faults called memory errors in the stored data, using parity bits or error correction codes. RAM of the read-only type, ROM, instead uses a metal mask to permanently enable/disable selected transistors, instead of storing a charge in them. Of special consideration are SIMM and DIMM memory modules.

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SRAM and DRAM are volatile. Other forms of computer storage, such as disks and magnetic tapes, have been used as persistent storage. Many newer products instead rely on flash memory to maintain data when not in use, such as PDAs or small music players. Certain personal computers, such as many rugged computers and netbooks, have also replaced magnetic disks with flash drives. With flash memory, only the NOR type is capable of true random access, allowing direct code execution, and is therefore often used instead of ROM; the lower cost NAND type is commonly used for bulk storage in memory cards and solid-state drives. A memory chip is an integrated circuit (IC) made of millions of transistors and capacitors. In the most common form of computer memory, dynamic random access memory (DRAM), a transistor and a capacitor are paired to create a memory cell, which represents a single bit of data. The capacitor holds the bit of information – a 0 or a 1 . The transistor acts as a switch that lets the control circuitry on the memory chip read the capacitor or change its state.

Random access memory, better known as RAM, stores data to be processed by the computer’s central processing unit. There are several types of RAM available to consumers for use in desktop and notebook computers, as well as netbooks and tablet computers. There are major differences between the types of RAM.


SDRAM, or Synchronous Dynamic Random Access Memory, is one of the earliest types of memory. SDRAM syncs with the system bus and will wait for a clock signal before responding to input. This was the first memory type able to accept tasks before it had finished the current task. This type of memory has become obsolete due to the more efficient Double Data Rate SDRAM types.


DDR SDRAM, for Double Data Synchronous Dynamic Random Access Memory, has superseded the original SDRAM. This type of RAM accepts data transfers on both edges of the clock cycle, consequently doubling the data throughput of the memory. DDR better conserves power and creates less heat than SDRAM, which made it preferable in early laptop designs.


DDR2 SDRAM is the successor to DDR SDRAM. The memory sticks are smaller and consume less power compared with DDR. DDR2 processes 64 bits twice in one clock cycle, which also trumps DDR in terms of speed. DDR2 memory sticks and slots are not compatible with DDR and DDR3 SDRAM.


Double Data Rate 3 Synchronous Dynamic Random Access Memory supersedes all previous SD and DDR types. DDR3 consumes less power and has double the output of DDR2. It has an increased clock rate and a doubled prefetch buffer to aid performance. DDR3 memory sticks and slots are not cross-compatible with DDR2 and DDR sticks and slots.

The only type of memory you need to purchase and install is DRAM. The other types are built in to the motherboard (ROM); processor (SRAM); and other components such as the video card, hard drives, and so on.


Read-only memory, or ROM, is a type of memory that can permanently or semipermanently store data. It is called read-only because it is either impossible or difficult to write to. ROM also is often referred to as nonvolatile memory because any data stored in ROM remains there, even if the power is turned off. As such, ROM is an ideal place to put the PC’s startup instructionsthat is, the software that boots the system.

Note that ROM and RAM are not opposites, as some people seem to believe. Both are simply types of memory. In fact, ROM could be classified as technically a subset of the system’s RAM. In other words, a portion of the system’s random access memory address space is mapped into one or more ROM chips. This is necessary to contain the software that enables the PC to boot up; otherwise, the processor would have no program in memory to execute when it was powered on.

The main ROM BIOS is contained in a ROM chip on the motherboard, but there are also adapter cards with ROMs on them as well. ROMs on adapter cards contain auxiliary BIOS routines and drivers needed by the particular card, especially for those cards that must be active early in the boot process, such as video cards. Cards that don’t need drivers active at boot time typically don’t have a ROM because those drivers can be loaded from the hard disk later in the boot process.

Most systems today use a type of ROM called electrically erasable programmable ROM (EEPROM), which is a form of Flash memory. Flash is a truly nonvolatile memory that is rewritable, enabling users to easily update the ROM or firmware in their motherboards or any other components (video cards, SCSI cards, peripherals, and so on).


Dynamic RAM (DRAM) is the type of memory chip used for most of the main memory in a modern PC. The main advantages of DRAM are that it is very dense, meaning you can pack a lot of bits into a very small chip, and it is inexpensive, which makes purchasing large amounts of memory affordable.

The memory cells in a DRAM chip are tiny capacitors that retain a charge to indicate a bit. The problem with DRAM is that it is dynamic. Also, because of the design, it must be constantly refreshed; otherwise, the electrical charges in the individual memory capacitors will drain and the data will be lost. Refresh occurs when the system memory controller takes a tiny break and accesses all the rows of data in the memory chips. Most systems have a memory controller (normally built in to the North Bridge portion of the motherboard chipset or located within the CPU in the case of the AMD Athlon 64 and Opteron processors), which is set for an industry-standard refresh time of 15ms (milliseconds). This means that every 15ms, all the rows in the memory are automatically read to refresh the data.

Refreshing the memory unfortunately takes processor time away from other tasks because each refresh cycle takes several CPU cycles to complete. In older systems, the refresh cycling could take up to 10% or more of the total CPU time, but with modern systems running in the multi-gigahertz range, refresh overhead is now on the order of a fraction of a percent or less of the total CPU time. Some systems allow you to alter the refresh timing parameters via the CMOS Setup. The time between refresh cycles is known as tREF and is expressed not in milliseconds, but in clock cycles

It’s important to be aware that increasing the time between refresh cycles (tREF) to speed up your system can allow some of the memory cells to begin draining prematurely, which can cause random soft memory errors to appear.

A soft error is a data error that is not caused by a defective chip. To avoid soft errors, it is usually safer to stick with the recommended or default refresh timing. Because refresh consumes less than 1% of modern system overall bandwidth, altering the refresh rate has little effect on performance. It is almost always best to use default or automatic settings for any memory timings in the BIOS Setup. Many modern systems don’t allow changes to memory timings and are permanently set to automatic settings. On an automatic setting, the motherboard reads the timing parameters out of the serial presence detect (SPD) ROM found on the memory module and sets the cycling speeds to match.

DRAMs use only one transistor and capacitor pair per bit, which makes them very dense, offering more memory capacity per chip than other types of memory. Currently, DRAM chips are available with densities of up to 1Gb or more. This means that DRAM chips are available with one billion or more transistors! Compare this to a Pentium D, which has 230 million transistors, and it makes the processor look wimpy by comparison. The difference is that in a memory chip, the transistors and capacitors are all consistently arranged in a (normally square) grid of simple repetitive structures, unlike the processor, which is a much more complex circuit of different structures and elements interconnected in a highly irregular fashion.

The transistor for each DRAM bit cell reads the charge state of the adjacent capacitor. If the capacitor is charged, the cell is read to contain a 1; no charge indicates a 0. The charge in the tiny capacitors is constantly draining, which is why the memory must be refreshed constantly. Even a momentary power interruption, or anything that interferes with the refresh cycles, can cause a DRAM memory cell to lose the charge and therefore the data. If this happens in a running system, it can lead to blue screens, global protection faults, corrupted files, and any number of system crashes.

DRAM is used in PC systems because it is inexpensive and the chips can be densely packed, so a lot of memory capacity can fit in a small space. Unfortunately, DRAM is also slow, typically much slower than the processor. For this reason, many types of DRAM architectures have been developed to improve performance.

Cache memory: sram

Another distinctly different type of memory exists that is significantly faster than most types of DRAM. SRAM stands for static RAM, which is so named because it does not need the periodic refresh rates like DRAM. Because of how SRAMs are designed, not only are refresh rates unnecessary, but SRAM is much faster than DRAM and much more capable of keeping pace with modern processors.

SRAM memory is available in access times of 2ns or less, so it can keep pace with processors running 500MHz or faster. This is because of the SRAM design, which calls for a cluster of six transistors for each bit of storage. The use of transistors but no capacitors means that refresh rates are not necessary because there are no capacitors to lose their charges over time. As long as there is power, SRAM remembers what is stored. With these attributes, why don’t we use SRAM for all system memory? The answers are simple.

Compared to DRAM, SRAM is much faster but also much lower in density and much more expensive. The lower density means that SRAM chips are physically larger and store fewer bits overall. The high number of transistors and the clustered design mean that SRAM chips are both physically larger and much more expensive to produce than DRAM chips. For example, a DRAM module might contain 64MB of RAM or more, whereas SRAM modules of the same approximate physical size would have room for only 2MB or so of data and would cost the same as the 64MB DRAM module. Basically, SRAM is up to 30 times larger physically and up to 30 times more expensive than DRAM. The high cost and physical constraints have prevented SRAM from being used as the main memory for PC systems

Year by year, the cost of computer systems continues to drop dramatically while the performance and capacity of the systems continue to rise equally dramatically. Find out and write about the evolution of microprocessor system. Give an example to support your answer.

Computer memory is one of the technologies that are used to store information in electronic device. Compare the various types of memory in terms of capacity, performance, access methods, physical types, and characteristics.



Introduction Of Question 1

Main Body Of Question 1

Conclusion Of Question 1

Introduction Of Question 2

Main Body Of Question 2

Conclusion Of Question 2



The microprocessor or the processor is the heart for the computer and it performs all the computational tasks, calculations and data processing etc inside the computer.  Microprocessor is the brain of the computer. In the computers, the most popular type of the processor is the Intel Pentium chip and the Pentium 1V is the latest chip by the Intel Corporation.  The microprocessors can be classified based on the following features.

The speed of the microprocessor is measured in the MHz or GHz.  This processor is also known as the CPU (Central Processing Unit).   It contains the control unit and the arithmetic unit and both works together to process the commands.  CPU is used in every computer whether it is a workstation, server or the laptop.  CPU is the complete computational engine that is designed as the chip.  It starts the work when you turn on your computer. 

CPU is designed to perform the arithmetic and logical operations inside the computer.  Common operations inside the computer include adding, subtracting, multiplying, comparing the values and fetching the different numbers to process them.  The higher the CPU clocks’ speed the more efficient will be the performance for the computer. 

Internal memory is that temporarily memories data while programs are running. Internal memory uses micro conductors, i.e. fast specialized electronic circuits. Internal memory corresponds to what we call random access memory (RAM).

External memory that stores information over the long term, including after the computer have been turned off. External memory corresponds to magnetic storage devices such as the hard drive, optical storage devices such as CD-ROMs and DVD-ROMs, as well as read-only memories (ROM).


I have understood the question 1 to find out what is microprocessor and for question 2 finding what is memory. In the solution it tells how about the microprocessors have been produced.


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