Long-Term Memory, Disk Drives, Optical Storage Dr. Harold D. Camp IT 212 002 1 March 2007.

Long-Term Memory, Disk Drives, Optical Storage

Dr. Harold D. Camp

IT 212 002

1 March 2007

Volatile or Non-Volatile

• Volatile memory does not retain its information without constand power• Needs refresh

• Non-Volatile maintains information indefinitely

Long-Term Storage Old & New

History

History

History

How Magnetic Storage Works• Media used in removable magnetic-storage devices is coated with iron oxide

• A ferromagnetic material

• If you expose it to a magnetic field it is permanently magnetized

• The media is typically called a disk or a cartridge

• The drive uses a motor to rotate the media at a high speed

• Accesses (reads) the stored information using small devices called heads

• Each head has a tiny electromagnet (an iron core wrapped with wire)

• The electromagnet applies a magnetic flux to the oxide on the media

• The oxide permanently "remembers" the flux last saw

• During writing, data signal sent through a coil to create a magnetic field

• At the gap, the magnetic flux forms a fringe pattern

• The flux magnetizes the oxide on the media

• During reading, the read head pulls a varying magnetic field across the gap

• Creates a varying magnetic field in the core and a signal in the coil

How Optical Storage Works

How Optical Storage Works• Media used in removable magnetic-storage devices is coated with iron oxide

• A ferromagnetic material

• If you expose it to a magnetic field it is permanently magnetized

• The media is typically called a disk or a cartridge

• The drive uses a motor to rotate the media at a high speed

• Accesses (reads) the stored information using small devices called heads

• Each head has a tiny electromagnet (an iron core wrapped with wire)

• The electromagnet applies a magnetic flux to the oxide on the media

• The oxide permanently "remembers" the flux last saw

• During writing, data signal sent through a coil to create a magnetic field

• At the gap, the magnetic flux forms a fringe pattern

• The flux magnetizes the oxide on the media

• During reading, the read head pulls a varying magnetic field across the gap

• Creates a varying magnetic field in the core and a signal in the coil

Mid-Term

• 8 March 2007

• Topics• History• Functions of a computer & terminology• Hardware & Operation• Busses, memory, and device access

First Electronic Computers

• Notable achievements include:

• The secret British Colossus computer (1944), had limited programmability

• Demonstrated that a device using thousands of tubes could be reasonably reliable and electronically reprogrammable.

– It was used for breaking German wartime codes.

• The Harvard Mark I (1944), a large-scale electromechanical computer with limited programmability.

• The US Army's Ballistics Research Laboratory ENIAC (1946),

– Used decimal arithmetic

– First general purpose electronic computer,

– Required rewiring to change its programming.

• EDSAC: first computer to implement the stored program (von Neumann) architecture (1952).

– John von Neumann

Once Von Neuman invented stored program, Rest Was History

EDSAC was one of the first computers

to implement the stored program (

von Neumann) architecture.

Microprocessors are miniaturized

devices that often implement stored

program CPUs.

• Modern computers implement the stored program architecture• The single trait by which the word "computer" is now defined. • Technologies used in computers have changed dramatically since the first electronic,

general-purpose computers of the 1940s• Most still use the von Neumann architecture. • The design made the universal computer a practical reality.

Evolving Technology

• Vacuum tube-based computers were in use throughout the 1950s,

• Replaced in the 1960s by transistor-based devices,

• Smaller, faster, cheaper, less power and more reliable.

• By the 1970s, integrated circuit technology

• Creation of microprocessors such as the Intel 4004

• Leap in size, speed, cost and reliability.

• By the 1980s, computers became sufficiently small and cheap to replace simple mechanical controls in domestic appliances

• Computers became widely accessible for personal use by individuals

• Home computers and personal computers.

• Widespread growth of the Internet since the 1990s,

• Personal computers are became as common as the television and the telephone

• Almost all modern electronic devices contain a computer.

Evolving Technology

Four Functions of a ComputerA computer has four functions:

a. accepts data Input

       The Information Processing

Cycle

b. processes data ProcessingProcessing c. produces output Output d. stores results Storage

ProcessorInput Output

Storage

Terminology

Some Beginning Terms• Hardware: the physical parts of the compute• Software: the programs (instructions) that tell

the computer what to do• Data: individual facts like first name, price,

quantity ordered• Information: data which has been massaged

into a useful form, like a complete mailing address

PC Hardware

MotherboardA typical computer is built with the microprocessor, main memory, and other

basic components on the motherboard. Other components of the computer such as external storage, control circuits for video display and sound, and peripheral devices are typically attached to the motherboard via ribbon cables, other cables, and power connectors.

A typical motherboard provides attachment points for one or more of the following: CPU, graphics card, sound card, hard disk controller, memory (RAM), and external peripheral devices. The connectors for external peripherals are nearly always color coded according to the PC 99 specification.

Power Supply

Power supplies, often referred to as "switching power supplies", use switcher technology to convert the AC input to lower DC voltages. The typical voltages supplied are:

3.3 volts 5 volts 12 volts

The 3.3- and 5-volts are typically used by digital circuits, while the 12-volt is used to run motors in disk drives and fans.

Case

Cases usually come with room for a power supply unit, several expansion slots and expansion bays, wires for powering up a

computer and some with built in I/O ports that must be connected to a motherboard.

Motherboards are screwed to the bottom or the side of the case, its I/O ports being exposed on the back of the case. Usually the

power supply unit is at the top of the case attached with several screws. The typical case has four 5.25" and three 3.5" expansion

bays for devices such as hard drives, floppy disk drives and CD-ROMs. A power button and sometimes a reset button are usually

located on the front. LED status lights for power and hard drive activity are often located near the power button and are powered from

wires that are connected with the motherboard. Some cases come with status monitoring equipment such as case temperature or

processor speed monitors.

Disk Drive

# Capacity, usually quoted in gigabytes. (older hard disks used to quote their smaller capacities in megabytes)

# Physical size, usually quoted in inches:

* Almost all hard disks today are of either the 3.5" or 2.5" varieties, used in desktops and laptops, respectively.

IDE Controller

Built into the motherboard, two connections provide for ribbon cables that send signals controlling disk drives

PCI Expansion Slot

The Peripheral Component Interconnect, or PCI Standard (in practice almost always shortened to PCI) specifies a computer bus for attaching peripheral devices to a computer motherboard. These devices can take any one of the following forms:

An integrated circuit fitted onto the motherboard itself, called a planar device in the PCI specification.

An expansion card that fits in sockets.

Random Access Memory (RAM)Random access memory (usually known by its acronym,

RAM) is a type of data store used in computers. It takes the form of integrated circuits that allow the stored data to be accessed in any order — that is, at random and without the physical movement of the storage medium or a physical reading head.

The word "random" refers to the fact that any piece of data can be returned quickly, and in a constant time, regardless of its physical location and whether or not it is related to the previous piece of data. This contrasts with storage mechanisms such as tapes, magnetic disks and optical disks, which rely on the physical movement of the recording medium or a reading head. In these devices, the movement takes longer than the data transfer, and the retrieval time varies depending on the physical location of the next item.

Basic Input/Output System

BIOS, in computing, stands for Basic Input/Output System also incorrectly known as Basic Integrated Operating System. BIOS refers to the firmware code run by a computer when first powered on. The primary function of the BIOS is to prepare the machine so other software programs stored on various media (such as hard drives, floppies, and CDs) can load, execute, and assume control of the computer. This process is known as booting up.

BIOS can also be said to be a coded program embedded on a chip that recognises and controls various devices that make up the computer. The term BIOS is specific to personal computer vendors. Among other classes of computers, the generic terms boot monitor, boot loader or boot ROM are commonly used.

MicroprocessorA microprocessor (sometimes abbreviated µP)

is a programmable digital electronic component that incorporates the functions of a central processing unit (CPU) on a single semiconducting integrated circuit (IC). The microprocessor was born by reducing the word size of the CPU from 32 bits to 4 bits, so that the transistors of its logic circuits would fit onto a single part. One or more microprocessors typically serve as the CPU in a computer system, embedded system, or handheld device.

Universal Serial Bus (USB)Universal Serial Bus (USB) is a serial bus

standard to interface devices. It was originally designed for computers, but its popularity has prompted it to also become commonplace on video game consoles, PDAs, portable DVD and media players, cellphones; and even devices such as televisions, home stereo equipment (e.g., digital audio players), car stereos and portable memory devices.

The radio spectrum based USB implementation is known as Wireless USB.

Network Connector

An electrical connector is a device for joining electrical circuits together. The connection may be temporary, as for portable equipment, or may require a tool for assembly and removal, or may be a permanent electrical joint between two wires or devices. There are hundreds of types of electrical connectors. In computing, an electrical connector can also be known as a physical interface.

Parallel Port

A parallel port is a type of socket found on personal computers for interfacing with various peripherals. It is also known as a printer port or Centronics] port. The IEEE 1284 standard defines the bi-directional version of the port.

For the most part, the USB interface has replaced the Centronics-style parallel port — as of 2006, most modern printers are connected through a USB connection, and often don't even have a parallel port connection. On many modern computers, the parallel port is omitted for cost savings, and is considered to be a legacy port. In laptops, access to a parallel port is still commonly available through docking stations.

Serial PortIn computing, a serial port is a serial communication physical interface through which

information transfers in or out one bit at a time (contrast parallel port). Throughout most of the history of personal computers, data transfer through serial ports connected the computer to devices such as terminals or modems. Mice, keyboards, and other peripheral devices also connected in this way.

While such interfaces as Ethernet, FireWire, and USB all send data as a serial stream, the term "serial port" usually identifies hardware more or less compliant to the RS-232 standard, intended to interface with a modem or with a similar communication device.

For the most part, the USB interface has replaced the serial port — as of 2006, most modern computers are connected to devices through a USB connection, and often don't even have a serial port connection. The serial port is omitted for cost savings, and is considered to be a legacy port.

Keyboard

A computer keyboard is a peripheral partially modeled after the typewriter keyboard. Keyboards are designed for the input of text and characters and also to control the operation of a computer

Operating System

An operating system (OS) is a computer program that manages the hardware and software resources of a computer. At the foundation of all system software, the OS performs basic tasks such as controlling and allocating memory, prioritizing system requests, controlling input and output devices, facilitating networking, and managing files. It also may provide a graphical user interface for higher level functions. It forms a platform for other software.

Services• Process Management• Disk and File Management• Internal/External Security• Networking• Graphical User Interfaces (GUI)• Device Drivers

Microsoft Windows OSThe Microsoft Windows family of operating systems originated as a graphical layer on

top of the older MS-DOS environment for the IBM PC. Modern versions are based on the newer Windows NT core that first took shape in OS/2 and borrowed from VMS. Windows runs on 32-bit and 64-bit Intel and AMD processors, although earlier versions also ran on the DEC Alpha, MIPS, Fairchild (later Intergraph) Clipper and PowerPC architectures (some work was done to port it to the SPARC architecture).

As of 2006, Windows held a near-monopoly of around 94% of the worldwide desktop market share, although some predict this to dwindle due to the increased interest in open source operating systems.[1] It is also used on low-end and mid-range servers, supporting applications such as web servers and database servers. In recent years, Microsoft has spent significant marketing and R&D money to demonstrate that Windows is capable of running any enterprise application which has resulted in consistent price/performance records (see the TPC) and significant acceptance in the enterprise market at the cost of existing Unix based system market share.

Plug and Play Architecture

Plug and Play Driver InstallationWhen a hardware device is connected — as when

you plug a USB camera into a USB port — Plug and Play Manager goes through the following steps to install the device.

1. After receiving an insertion interrupt, Plug and Play Manager checks what hardware resources the device needs

• memory ranges, I/O ranges, and DMA channels. Plug and Play Manager then assigns those resources.

2. Plug and Play Manager checks the hardware identification number of the device.

3. Plug and Play Manager then checks the hard drive, floppy drives, CD-ROM drives, and Windows Update for drivers that match the number of the device.

4. If multiple drivers are found, Plug and Play Manager chooses the driver that is the best match by looking for the closest hardware ID or compatible ID match, driver signatures, and other driver features.

5. Plug and Play Manager then installs the best-match driver and the operating system starts the device.

Bus Connections

• A typical PC today has two main buses:• System or local bus

• Connects the microprocessor (CPU) and the system memory

• Fastest bus in the system• A slower bus for communicating with hard

disks and sound cards• Connect to the system bus through a

bridge, part of the computer's chipset • Acts as a traffic cop

• A bus makes parts more interchangeable• If you want a better graphics card

• Unplug the old card from the bus • Plug in a new one

• If you want two monitors on your computer• Plug two graphics cards into the bus

PCI Bus

• There are other buses as well• Universal Serial Bus (USB)

• Connects things like cameras, scanners and printers

• A thin wire to connect to the devices• Many devices can share that wire

simultaneously• Firewire is another bus

• Used mostly for video cameras & external hard drives

• Along came PCI• Early 1990s, Intel introduced a new bus standard • Peripheral Component Interconnect (PCI) bus• A hybrid between ISA and VL-Bus• Direct access to system memory for connected devices• Uses a bridge to connect to the system bus and the CPU• Capable of even higher performance than VL-Bus and• Eliminates interference with the CPU

• The system bus physically connects the processor to most of the other components in the computer

• Including main memory (RAM), hard drives and PCI slots• The system bus usually operates at 400-MHz to 800-MHz.

Backside Bus• The backside bus

• A separate connection between the processor and the Level 2 cache

• Operates faster than frontside bus

• Same speed as the processor• Caching works efficiently as

possible. • Backside buses evolved over

years• In 1990s, backside bus was a

wire • Connected CPU to an off-chip

cache• Cache was a separate chip • Required expensive memory

• Since then, the Level 2 cache is integrated into the microprocessor• Smaller and cheaper

PC Memory

• PC computer memory is divided into segments,• 64 kilobytes each (65,536 bytes, to be exact)• Segment register in microprocessor indicates

segment is to be accessed• Segment 0

• Contains memory pointers, device drivers, buffers, input/output ports, and other essential information required by the computer and its operating system

• Segment 0 contains 65,536 memory addresses• Figures on next pages show how different

portions of memory are allocated

What is Plug ‘n Play• With Plug and Play under Microsoft Windows Server 2003

• Connect a hardware device to your system • Leave the job of configuring and starting the device to the operating system• Plug and Play in Windows Server 2003 supports a wide range of devices

• In Windows Server 2003• Plug and Play support is optimized for computers that include an Advanced Configuration

and Power Interface (ACPI) BIOS• Defined by Advanced Configuration and Power Interface (ACPI) Specification• Hardware and software interface specification • Combines and enhances Plug and Play and Advanced Power Management (APM)

standards• ACPI devices include low-level system devices (batteries)

• On x86-based computers• Interaction between the BIOS and Plug and Play depends on whether the system BIOS or

the operating system configures the hardware• Plug and Play detection runs with logon process

• Relies on system firmware, hardware, device drivers, and operating system features to detect and enumerate new devices

• ACPI firmware provides enhanced features, such as hardware resource sharing• When Plug and Play components are coordinated, Windows Server 2003 can detect new

devices, allocate system resources, and install or request drivers with minimal user intervention.

The Windows Registry • Every operating system and application needs a place to store

configuration settings and user preferences• MS-DOS uses CONFIG.SYS• DOS programs had to make their own arrangements for storing user settings

• Windows originally used INI files • Read and written using special routines available to Windows programs• Windows had one configuration file, SYSTEM.INI• Used for all the internal settings • Plus another, WIN.INI, for user preferences• Each application had an INI file• INI files were slow to access and limited to 64Kb• Unsuited for the 32-bit versions of Windows

• So for Windows NT and Windows 95 Microsoft introduced the Registry• A database for storing and accessing configuration data• Organized for fast and efficient access• Data is stored in a hierarchical manner like the folders on a hard disk• Registry data that is currently in use is cached to provide better performance

• http://www.tech-pro.net/intro_reg.html

PC Memory• Figures 3 and 4

• Each colored line contains the mean value of one 256 byte page of memory

• Colored bands make it easier to see how different portions are allocated for different uses

• For instance, the blue-green and green blocks appear to be for data storage, since the buffers are located there

• Gray areas correspond to the areas where machine code is located

• The dotted lines in the gray zones that resulted from conversion from bitmap to gif format

How do Operating Systems Work?

http://www.howstuffworks.com/operating-system.htm

Windows in particular