Microprocessor lecture

1. Microprocessor - electronic circuit that functions as the central processing unit (CPU)
of a computer, providing computational control. Microprocessors are also used in other
advanced electronic systems, such as computer printers, automobiles, and jet airliners.
The most complicated ICs. They are composed of millions of transistors that have been
configured as thousands of individual digital circuits, each of which performs some
specific logic function. A microprocessor is built entirely of these logic circuits
synchronized to each other. Just like marching band, the circuits perform their logic
function only on direction by the bandmaster.
The BANDMASTER in a microprocessor, so to speak, is called the clock. The CLOCK
is a signal that quickly alternates between two logic states. Every time the clock changes
states, every logic circuit in the microprocessor does something. Calculations can be
made very quickly, depending on the speed (“clock frequency”) of the microprocessor.
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The microprocessor is one type of ultra-large-scale integrated circuit.
Integrated circuits, also known as microchips or chips, are complex electronic circuits
consisting of extremely tiny components formed on a single, thin, flat piece of material
known as a semiconductor. Modern microprocessors incorporate transistors (which act
as electronic amplifiers, oscillators, or, most commonly, switches), in addition to other
components such as resistors, diodes, capacitors, and wires, all packed into an area about
the size of a postage stamp.

2. HISTORY OF MICROPROCESSOR
The first microprocessor was the Intel 4004, produced in 1971. Originally developed for
a calculator, and revolutionary for its time, it contained 2,300 transistors on a 4-bit
microprocessor that could perform only 60,000 operations per second. The first 8-bit
microprocessor was the Intel 8008, developed in 1972 to run computer terminals. The
Intel 8008 contained 3,300 transistors. The first truly general-purpose microprocessor,
developed in 1974, was the 8-bit Intel 8080 (see Microprocessor, 8080), which
contained 4,500 transistors and could execute 200,000 instructions per second. By 1989,
32-bit microprocessors containing 1.2 million transistors and capable of executing 20
million instructions per second had been introduced.
In the 1990s the number of transistors on microprocessors continued to double nearly
every 18 months. The rate of change followed an early prediction made by American
semiconductor pioneer Gordon Moore. In 1965 Moore predicted that the number of
transistors on a computer chip would double every year, a prediction that has come to be
known as Moore’s Law. In the mid-1990s chips included the Intel Pentium Pro,
containing 5.5 million transistors; the UltraSparc-II, by Sun Microsystems, containing
5.4 million transistors; the PowerPC620, developed jointly by Apple, IBM, and
Motorola, containing 7 million transistors; and the Digital Equipment Corporation's
Alpha 21164A, containing 9.3 million transistors. By the end of the decade
microprocessors contained many millions of transistors, transferred 64 bits of data at
once, and performed billions of instructions per second.
SEMICONDUCTOR
All integrated circuits are fabricated from semiconductors, substances whose ability to
conduct electricity ranks between that of a conductor and that of a nonconductor, or
insulator. Silicon is the most common semiconductor material. Because the electrical
conductivity of a semiconductor can change according to the voltage applied to it,
transistors made from semiconductors act like tiny switches that turn electrical current
on and off in just a few nanoseconds (billionths of a second). This capability enables a
computer to perform many billions of simple instructions each second and to complete
complex tasks quickly.

3. The transistor used most commonly in the microelectronics industry is called a metal-
oxide semiconductor field-effect transistor (MOSFET). It contains two n-type regions,
called the source and the drain, with a p-type region in between them, called the channel.
Over the channel is a thin layer of nonconductive silicon dioxide topped by another
layer, called the gate. For electrons to flow from the source to the drain, a voltage
(forward bias) must be applied to the gate. This causes the gate to act like a control
switch, turning the MOSFET on and off and creating a logic gate that transmits digital 1s
and 0s throughout the microprocessor.
Computer System
A typical computer system consists of a central processing unit (CPU), input devices,
storage devices, and output devices. The CPU consists of an arithmetic/logic unit,
registers, control section, and internal bus. The arithmetic/logic unit carries out
arithmetical and logical operations. The registers store data and keep track of operations.

4. The control unit regulates and controls various operations. The internal bus connects the
units of the CPU with each other and with external components of the system. For most
computers, the principal input devices are a keyboard and a mouse. Storage devices
include hard disks, CD-ROM drives, and random access memory (RAM) chips. Output
devices that display data include monitors and printers.
Motherboard, in computer science, the main circuit board in a computer. The most
important computer chips and other electronic components that give function to a
computer are located on the motherboard. The motherboard is a printed circuit board that
connects the various elements on it through the use of traces, or electrical pathways. The
motherboard is indispensable to the computer and provides the main computing
capability.
Personal computers normally have one central processing unit (CPU), or
microprocessor, which is located with other chips on the motherboard. The manufacturer
and model of the CPU chip carried by the motherboard is a key criterion for designating
the speed and other capabilities of the computer. The CPU in many personal computers
is not permanently attached to the motherboard, but is instead plugged into a socket so
that it may be removed and upgraded.
Motherboards also contain important computing components, such as the basic
input/output system (BIOS), which contains the basic set of instructions required to
control the computer when it is first turned on; different types of memory chips such as
random access memory (RAM) and cache memory; mouse, keyboard, and monitor
control circuitry; and logic chips that control various parts of the computer’s function.
Having as many of the key components of the computer as possible on the motherboard
improves the speed and operation of the computer.
Users may expand their computer’s capability by inserting an expansion board into
special expansion slots on the motherboard. Expansion slots are standard with nearly all
personal computers and offer faster speed, better graphics capabilities, communication
capability with other computers, and audio and video capabilities. Expansion slots come
in either half or full size, and can transfer 8 or 16 bits (the smallest units of information
that a computer can process) at a time, respectively.
The pathways that carry data on the motherboard are called buses. The amount of data
that can be transmitted at one time between a device, such as a printer or monitor, and
the CPU affects the speed at which programs run. For this reason, buses are designed to
carry as much data as possible. To work properly, expansion boards must conform to bus
standards such as integrated drive electronics (IDE), Extended Industry Standard
Architecture (EISA), or small computer system interface (SCSI).