Note-Computer and Peripheral

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COMPUTER

&

PERIPHERAL


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MOTHERBOARD

A motherboard is the central or primary circuit board making up a complex electronic

system, such as a modern computer. It is also known as a mainboard, baseboard,

system board, or, on Apple computers, a logic board, and is sometimes abbreviated as

mobo.[1]

Most after-market motherboards produced today are designed for so-called IBM-

compatiblecomputers, which hold over 96% of thepersonal computermarket today.[2]

Motherboards for IBM-compatible computers are specifically covered in the PC

motherboardarticle.

The basic purpose of the motherboard, like abackplane, is to provide the electrical and

logical connections by which the other components of the system communicate.

A typical desktop computeris built with the microprocessor, main memory, and other

essential components on the motherboard. Other components such asexternal storage,

controllers forvideo display and sound, andperipheral devices are typically attached to

the motherboard via edge connectorsand cables, although in modern computers it is

increasingly common to integrate these "peripherals" into the motherboard.

Contents

1 Components and functionso 1.1 Integrated peripherals

2 History 3 Form factors

o 3.1 Visual comparison 4 See also 5 Notes

6 External links
http://en.wikipedia.org/wiki/Printed_circuit_boardhttp://en.wikipedia.org/wiki/Computerhttp://en.wikipedia.org/wiki/Apple_Inc.http://en.wikipedia.org/wiki/Logic_boardhttp://en.wikipedia.org/wiki/Logic_boardhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-0#_note-0http://en.wikipedia.org/wiki/IBM-compatiblehttp://en.wikipedia.org/wiki/IBM-compatiblehttp://en.wikipedia.org/wiki/IBM-compatiblehttp://en.wikipedia.org/wiki/Personal_computerhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-1#_note-1http://en.wikipedia.org/wiki/PC_motherboardhttp://en.wikipedia.org/wiki/PC_motherboardhttp://en.wikipedia.org/wiki/PC_motherboardhttp://en.wikipedia.org/wiki/Backplanehttp://en.wikipedia.org/wiki/Backplanehttp://en.wikipedia.org/wiki/Backplanehttp://en.wikipedia.org/wiki/Desktop_computerhttp://en.wikipedia.org/wiki/Microprocessorhttp://en.wikipedia.org/wiki/Primary_storagehttp://en.wikipedia.org/wiki/External_storagehttp://en.wikipedia.org/wiki/External_storagehttp://en.wikipedia.org/wiki/Video_cardhttp://en.wikipedia.org/wiki/Sound_cardhttp://en.wikipedia.org/wiki/Peripheralhttp://en.wikipedia.org/wiki/Edge_connectorhttp://en.wikipedia.org/wiki/Edge_connectorhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#Components_and_functions#Components_and_functionshttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#Integrated_peripherals#Integrated_peripheralshttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#History#Historyhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#Form_factors#Form_factorshttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#Visual_comparison#Visual_comparisonhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#See_also#See_alsohttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#Notes#Noteshttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#External_links#External_linkshttp://en.wikipedia.org/wiki/Printed_circuit_boardhttp://en.wikipedia.org/wiki/Computerhttp://en.wikipedia.org/wiki/Apple_Inc.http://en.wikipedia.org/wiki/Logic_boardhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-0#_note-0http://en.wikipedia.org/wiki/IBM-compatiblehttp://en.wikipedia.org/wiki/IBM-compatiblehttp://en.wikipedia.org/wiki/Personal_computerhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-1#_note-1http://en.wikipedia.org/wiki/PC_motherboardhttp://en.wikipedia.org/wiki/PC_motherboardhttp://en.wikipedia.org/wiki/Backplanehttp://en.wikipedia.org/wiki/Desktop_computerhttp://en.wikipedia.org/wiki/Microprocessorhttp://en.wikipedia.org/wiki/Primary_storagehttp://en.wikipedia.org/wiki/External_storagehttp://en.wikipedia.org/wiki/Video_cardhttp://en.wikipedia.org/wiki/Sound_cardhttp://en.wikipedia.org/wiki/Peripheralhttp://en.wikipedia.org/wiki/Edge_connectorhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#Components_and_functions#Components_and_functionshttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#Integrated_peripherals#Integrated_peripheralshttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#History#Historyhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#Form_factors#Form_factorshttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#Visual_comparison#Visual_comparisonhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#See_also#See_alsohttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#Notes#Noteshttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#External_links#External_links


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Components and functions

The 2004 K7VT4A Pro[3] motherboard by ASRock. The chipset on this board consists of

northbridge andsouthbridge chips.

The motherboard of a typical desktop consists of a largePCB. It holds electronic

components and interconnects, as well as physical connectors (sockets, slots, and

headers) into which other computer components may be inserted or attached.

Most motherboards include, at a minimum:

sockets in which one or more microprocessors (CPUs) are installed[4]

slots into which the system's main memory is installed (typically in the form of

DIMM modules containing DRAMchips)

achipset which forms an interface between the CPU's front-side bus, main

memory, and peripheralbuses

non-volatile memory chips (usually Flash ROM in modern motherboards)

containing the system'sfirmware orBIOS

aclock generatorwhich produces the system clock signal to synchronize the

various components

slots for expansion cards (these interface to the system via the buses supported by

the chipset)
http://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-2#_note-2http://en.wikipedia.org/wiki/ASRockhttp://en.wikipedia.org/wiki/Northbridge_(computing)http://en.wikipedia.org/wiki/Southbridge_(computing)http://en.wikipedia.org/wiki/Southbridge_(computing)http://en.wikipedia.org/wiki/Printed_circuit_boardhttp://en.wikipedia.org/wiki/Printed_circuit_boardhttp://en.wikipedia.org/wiki/Printed_circuit_boardhttp://en.wikipedia.org/wiki/Headerhttp://en.wikipedia.org/wiki/CPU_sockethttp://en.wikipedia.org/wiki/Microprocessorhttp://en.wikipedia.org/wiki/CPUhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-3#_note-3http://en.wikipedia.org/wiki/DIMMhttp://en.wikipedia.org/wiki/Dynamic_random_access_memoryhttp://en.wikipedia.org/wiki/Dynamic_random_access_memoryhttp://en.wikipedia.org/wiki/Chipsethttp://en.wikipedia.org/wiki/Chipsethttp://en.wikipedia.org/wiki/Front-side_bushttp://en.wikipedia.org/wiki/Bus_(computing)http://en.wikipedia.org/wiki/Non-volatile_memoryhttp://en.wikipedia.org/wiki/Flash_ROMhttp://en.wikipedia.org/wiki/Firmwarehttp://en.wikipedia.org/wiki/Firmwarehttp://en.wikipedia.org/wiki/BIOShttp://en.wikipedia.org/wiki/BIOShttp://en.wikipedia.org/wiki/Clock_generatorhttp://en.wikipedia.org/wiki/Clock_generatorhttp://en.wikipedia.org/wiki/Clock_signalhttp://en.wikipedia.org/wiki/Image:ASRock_K7VT4A_Pro_Mainboard_Labeled_English.pnghttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-2#_note-2http://en.wikipedia.org/wiki/ASRockhttp://en.wikipedia.org/wiki/Northbridge_(computing)http://en.wikipedia.org/wiki/Southbridge_(computing)http://en.wikipedia.org/wiki/Printed_circuit_boardhttp://en.wikipedia.org/wiki/Headerhttp://en.wikipedia.org/wiki/CPU_sockethttp://en.wikipedia.org/wiki/Microprocessorhttp://en.wikipedia.org/wiki/CPUhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-3#_note-3http://en.wikipedia.org/wiki/DIMMhttp://en.wikipedia.org/wiki/Dynamic_random_access_memoryhttp://en.wikipedia.org/wiki/Chipsethttp://en.wikipedia.org/wiki/Front-side_bushttp://en.wikipedia.org/wiki/Bus_(computing)http://en.wikipedia.org/wiki/Non-volatile_memoryhttp://en.wikipedia.org/wiki/Flash_ROMhttp://en.wikipedia.org/wiki/Firmwarehttp://en.wikipedia.org/wiki/BIOShttp://en.wikipedia.org/wiki/Clock_generatorhttp://en.wikipedia.org/wiki/Clock_signal


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power connectors and circuits, which receive electrical power from thecomputer

power supply and distribute it to the CPU, chipset, main memory, and expansion

cards.[5]

The Octek Jaguar V motherboard from 1993.[6] This board has 6 ISA slots but few

onboard peripherals, as evidenced by the lack of external connectors.

Additionally, nearly all motherboards include logic and connectors to support commonly-

used input devices, such asPS/2 connectorsfor amouse and keyboard. Earlypersonal

computers such as the Apple II orIBM PC included only this minimal peripheral support

on the motherboard. Additional peripherals such asdisk controllers and serial portswere

provided as expansion cards.

Given the high thermal design powerof high-speed computer CPUs and components,

modern motherboards nearly always include heatsinks and mounting points forfans to

dissipate excess heat.

Integrated peripherals
http://en.wikipedia.org/wiki/Computer_power_supplyhttp://en.wikipedia.org/wiki/Computer_power_supplyhttp://en.wikipedia.org/wiki/Computer_power_supplyhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-4#_note-4http://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-5#_note-5http://en.wikipedia.org/wiki/ISA_bushttp://en.wikipedia.org/wiki/PS/2_connectorhttp://en.wikipedia.org/wiki/PS/2_connectorhttp://en.wikipedia.org/wiki/PS/2_connectorhttp://en.wikipedia.org/wiki/Computer_mousehttp://en.wikipedia.org/wiki/Computer_mousehttp://en.wikipedia.org/wiki/Personal_computerhttp://en.wikipedia.org/wiki/Personal_computerhttp://en.wikipedia.org/wiki/Apple_IIhttp://en.wikipedia.org/wiki/IBM_PChttp://en.wikipedia.org/wiki/Disk_controllerhttp://en.wikipedia.org/wiki/Disk_controllerhttp://en.wikipedia.org/wiki/Serial_porthttp://en.wikipedia.org/wiki/Serial_porthttp://en.wikipedia.org/wiki/Thermal_Design_Powerhttp://en.wikipedia.org/wiki/Thermal_Design_Powerhttp://en.wikipedia.org/wiki/Heatsinkhttp://en.wikipedia.org/wiki/Computer_fanhttp://en.wikipedia.org/wiki/Computer_fanhttp://en.wikipedia.org/wiki/Image:386DX40_MB_Jaguar_V.jpghttp://en.wikipedia.org/wiki/Image:386DX40_MB_Jaguar_V.jpghttp://en.wikipedia.org/wiki/Computer_power_supplyhttp://en.wikipedia.org/wiki/Computer_power_supplyhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-4#_note-4http://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-5#_note-5http://en.wikipedia.org/wiki/ISA_bushttp://en.wikipedia.org/wiki/PS/2_connectorhttp://en.wikipedia.org/wiki/Computer_mousehttp://en.wikipedia.org/wiki/Personal_computerhttp://en.wikipedia.org/wiki/Personal_computerhttp://en.wikipedia.org/wiki/Apple_IIhttp://en.wikipedia.org/wiki/IBM_PChttp://en.wikipedia.org/wiki/Disk_controllerhttp://en.wikipedia.org/wiki/Serial_porthttp://en.wikipedia.org/wiki/Thermal_Design_Powerhttp://en.wikipedia.org/wiki/Heatsinkhttp://en.wikipedia.org/wiki/Computer_fan


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Diagram of a modern motherboard, which supports many on-board peripheral functions

as well as several expansion slots.

With the steadily declining costs and size ofintegrated circuits, it is now possible to

include support for many peripherals on the motherboard. By combining many functions

on one PCB, the physical size and total cost of the system may be reduced; highly-

integrated motherboards are thus especially popular insmall form factorand budget

computers.

For example, the ECS RS485M-M,[7] a typical modern budget motherboard for computers

based on AMDprocessors, has on-board support for a very large range of peripherals:

disk controllers for a floppy disk drive, up to 2 PATA drives, and up to 4SATA

drives (including RAID 0/1support)
http://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Small_form_factorhttp://en.wikipedia.org/wiki/Small_form_factorhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-6#_note-6http://en.wikipedia.org/wiki/Advanced_Micro_Deviceshttp://en.wikipedia.org/wiki/Advanced_Micro_Deviceshttp://en.wikipedia.org/wiki/Floppy_diskhttp://en.wikipedia.org/wiki/AT_Attachmenthttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/RAID#Standard_RAID_levelshttp://en.wikipedia.org/wiki/RAID#Standard_RAID_levelshttp://en.wikipedia.org/wiki/Image:Motherboard_diagram.pnghttp://en.wikipedia.org/wiki/Integrated_circuithttp://en.wikipedia.org/wiki/Small_form_factorhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-6#_note-6http://en.wikipedia.org/wiki/Advanced_Micro_Deviceshttp://en.wikipedia.org/wiki/Floppy_diskhttp://en.wikipedia.org/wiki/AT_Attachmenthttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/RAID#Standard_RAID_levels


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integrated ATIRadeon graphics controller supporting 2D and 3D graphics, with

VGA andTV output

integrated sound card supporting 6-channel audio and S/PDIF output

fast Ethernet network controllerfor 10/100 Mbit networking

USB 2.0 controller supporting up to 8 USB ports

IrDA controller for infrared data communication (e.g. with an IrDA enabled

Cellular Phone or Printer)

temperature, voltage, and fan-speed sensors that allow software to monitor the

health of computer components

Expansion cards to support all of these functions would have cost hundreds of dollars

even a decade ago, howeveras of April 2007such highly-integrated motherboards areavailable for as little as $30 in the USA.

History

Prior to the advent of the Apple II in 1977, a computer was usually built in a case or

mainframe with components connected by abackplane consisting of a set of slots

themselves connected with wires. The CPU, memory and I/O peripherals were housed on

individual PCBs or cards which plugged into the backplane.

A modern motherboard by Universal Abit (IN9 32X SLI).[8] Note the heatsinks for

cooling of motherboard components, and the large number of peripheral connectors and

components.
http://en.wikipedia.org/wiki/Integrated_Graphics#Integrated_graphics_solutionshttp://en.wikipedia.org/wiki/ATI_Technologieshttp://en.wikipedia.org/wiki/Radeonhttp://en.wikipedia.org/wiki/Video_Graphics_Arrayhttp://en.wikipedia.org/wiki/TV-outhttp://en.wikipedia.org/wiki/TV-outhttp://en.wikipedia.org/wiki/Sound_card#Integrated_sound_on_the_PChttp://en.wikipedia.org/wiki/S/PDIFhttp://en.wikipedia.org/wiki/Fast_Ethernethttp://en.wikipedia.org/wiki/Network_cardhttp://en.wikipedia.org/wiki/Megabithttp://en.wikipedia.org/wiki/Universal_Serial_Bushttp://en.wikipedia.org/wiki/Infrared_Data_Associationhttp://en.wikipedia.org/wiki/As_of_April_2007http://en.wikipedia.org/wiki/As_of_April_2007http://en.wikipedia.org/wiki/Apple_IIhttp://en.wikipedia.org/wiki/Mainframe_computerhttp://en.wikipedia.org/wiki/Backplanehttp://en.wikipedia.org/wiki/CPUhttp://en.wikipedia.org/wiki/CPUhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-7#_note-7http://en.wikipedia.org/wiki/Heatsinkhttp://en.wikipedia.org/wiki/Image:In9-32x-max_top_500.jpghttp://en.wikipedia.org/wiki/Integrated_Graphics#Integrated_graphics_solutionshttp://en.wikipedia.org/wiki/ATI_Technologieshttp://en.wikipedia.org/wiki/Radeonhttp://en.wikipedia.org/wiki/Video_Graphics_Arrayhttp://en.wikipedia.org/wiki/TV-outhttp://en.wikipedia.org/wiki/Sound_card#Integrated_sound_on_the_PChttp://en.wikipedia.org/wiki/S/PDIFhttp://en.wikipedia.org/wiki/Fast_Ethernethttp://en.wikipedia.org/wiki/Network_cardhttp://en.wikipedia.org/wiki/Megabithttp://en.wikipedia.org/wiki/Universal_Serial_Bushttp://en.wikipedia.org/wiki/Infrared_Data_Associationhttp://en.wikipedia.org/wiki/As_of_April_2007http://en.wikipedia.org/wiki/Apple_IIhttp://en.wikipedia.org/wiki/Mainframe_computerhttp://en.wikipedia.org/wiki/Backplanehttp://en.wikipedia.org/wiki/CPUhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#_note-7#_note-7http://en.wikipedia.org/wiki/Heatsink


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With the arrival of the microprocessor, it became more cost-effective to place the

backplane connectors, processor and glue logic onto a single "mother" board, with video,

memory and I/O functions on "child" cards hence the terms "motherboard" and

daughterboard. The Apple IIcomputer featured a motherboard with 8 expansion slots.

During the late 1980s and 1990s, it became economical to move an increasing number of

peripheral functions onto the motherboard (see above). In the late 1980s, motherboards

began to include single ICs (called Super I/Ochips) capable of supporting a set of low-

speed peripherals: keyboard, mouse, floppy disk drive, serial ports, and parallel ports. As

of the early 2000s, many motherboards support a full range of audio, video, storage, and

networking functions without the need for any expansion cards at all; higher-end systems

for 3D gaming and computer graphics typically retain only the graphics card as a separatecomponent.

The early pioneers of motherboard manufacturing were Micronics, Mylex, AMI, DTK,

Hauppauge, Orchid Technology, Elitegroup, DFI, and a number of Taiwan-based

manufacturers.

It can be argued that the motherboard industry was born by IBM in 1981 with the release

their entry level 5150 Personal Computer (IBM PC) which was based on a motherboard.The motherboard provided an Intel 4.77MHz 8088 with 16K bytes of on-board memory,

expandable to 640K through the use of plug-in memory boards, eight 8-bit ISA expansion

connectors, cassette tape port and keyboard port. All other I/O such as the interface for

160K 5-1/4" floppy drives, serial and parallel ports were provided by plug-in boards.

IBM approached Digital Research about using DR/DOS as an operating system but was

rebuffed. IBM approached Microsoft and licensed PC-DOS. Microsoft released PC-DOS

1.1 in 1982 by retaining rights to the operating system allowing them to sell it to other

manufacturers.

IBM published the schematics and I/O map allowing the birth of the clone motherboard

industry.
http://en.wikipedia.org/wiki/Glue_logichttp://en.wikipedia.org/wiki/Daughterboardhttp://en.wikipedia.org/wiki/Daughterboardhttp://en.wikipedia.org/wiki/Apple_IIhttp://en.wikipedia.org/wiki/Apple_IIhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#Integrated_peripherals#Integrated_peripheralshttp://en.wikipedia.org/wiki/Super_I/Ohttp://en.wikipedia.org/wiki/Super_I/Ohttp://en.wikipedia.org/wiki/Computer_graphicshttp://en.wikipedia.org/wiki/Glue_logichttp://en.wikipedia.org/wiki/Daughterboardhttp://en.wikipedia.org/wiki/Apple_IIhttp://f/Komputer/Wikipedia%20English/motherboard/Motherboard.htm#Integrated_peripherals#Integrated_peripheralshttp://en.wikipedia.org/wiki/Super_I/Ohttp://en.wikipedia.org/wiki/Computer_graphics


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Form factors

Main article:PC motherboard

Motherboards are produced in a variety ofform factors, some of which are specific to

individual computer manufacturers. However, the motherboards used in IBM-compatible

commodity computers have been standardized to fit various case sizes. As of 2007, most

desktop computermotherboards use one of these standard form factorseven those

found in Macintosh andSun computers which have not traditionally been built from

commodity components.

These are some of the more popular motherboard form factors:

It has been suggested that this article or section be merged intocomparison of computer

form factors. (Discuss)

PC/XT - created by IBM for the IBM PC, its first home computer. As the

specifications were open, many clonemotherboards were produced and it became

ade facto standard.

AT form factor(Advanced Technology) - created by IBM for its PC/XT

successor, the AT. Also known as Full AT, it was popular during the era of the

Intel 80386 microprocessor. Superseded by ATX.

Baby AT - IBM's 1985 successor to the AT motherboard. Functionally equivalent

to the AT, it became popular due to its significantly smaller size. ATX - created by Intel in 1995.As of 2007, it is the most popular form factor for

commodity motherboards. Typical size is 9.6x12" although some companies

extend that to 10x12".

EATX - Refers to Extended ATX with a size of 13x12". Typically used for Server

Class type motherboards with dual processors and too much circuitry for a
http://en.wikipedia.org/wiki/PC_motherboardhttp://en.wikipedia.org/wiki/Form_factorhttp://en.wikipedia.org/wiki/Form_factorhttp://en.wikipedia.org/wiki/List_of_motherboard_manufacturers#Motherboardshttp://en.wikipedia.org/wiki/Commodity_computerhttp://en.wikipedia.org/wiki/Computer_casehttp://en.wikipedia.org/wiki/As_of_2007http://en.wikipedia.org/wiki/As_of_2007http://en.wikipedia.org/wiki/Desktop_computerhttp://en.wikipedia.org/wiki/Macintoshhttp://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Wikipedia:Merging_and_moving_pageshttp://en.wikipedia.org/wiki/Comparison_of_computer_form_factorshttp://en.wikipedia.org/wiki/Comparison_of_computer_form_factorshttp://en.wikipedia.org/wiki/Comparison_of_computer_form_factorshttp://en.wikipedia.org/wiki/Talk:Comparison_of_computer_form_factorshttp://en.wikipedia.org/wiki/IBM_PC_XThttp://en.wikipedia.org/wiki/IBM_PChttp://en.wikipedia.org/wiki/IBM_PChttp://en.wikipedia.org/wiki/Clone_(computer_science)http://en.wikipedia.org/wiki/Clone_(computer_science)http://en.wikipedia.org/wiki/De_factohttp://en.wikipedia.org/wiki/De_factohttp://en.wikipedia.org/wiki/AT_form_factorhttp://en.wikipedia.org/wiki/IBM_PC_AThttp://en.wikipedia.org/wiki/Intel_80386http://en.wikipedia.org/wiki/AT_(form_factor)#Variantshttp://en.wikipedia.org/wiki/ATXhttp://en.wikipedia.org/wiki/As_of_2007http://en.wikipedia.org/wiki/As_of_2007http://en.wikipedia.org/wiki/EATXhttp://en.wikipedia.org/wiki/PC_motherboardhttp://en.wikipedia.org/wiki/Form_factorhttp://en.wikipedia.org/wiki/List_of_motherboard_manufacturers#Motherboardshttp://en.wikipedia.org/wiki/Commodity_computerhttp://en.wikipedia.org/wiki/Computer_casehttp://en.wikipedia.org/wiki/As_of_2007http://en.wikipedia.org/wiki/Desktop_computerhttp://en.wikipedia.org/wiki/Macintoshhttp://en.wikipedia.org/wiki/Sunhttp://en.wikipedia.org/wiki/Wikipedia:Merging_and_moving_pageshttp://en.wikipedia.org/wiki/Comparison_of_computer_form_factorshttp://en.wikipedia.org/wiki/Comparison_of_computer_form_factorshttp://en.wikipedia.org/wiki/Talk:Comparison_of_computer_form_factorshttp://en.wikipedia.org/wiki/IBM_PC_XThttp://en.wikipedia.org/wiki/IBM_PChttp://en.wikipedia.org/wiki/Clone_(computer_science)http://en.wikipedia.org/wiki/De_factohttp://en.wikipedia.org/wiki/AT_form_factorhttp://en.wikipedia.org/wiki/IBM_PC_AThttp://en.wikipedia.org/wiki/Intel_80386http://en.wikipedia.org/wiki/AT_(form_factor)#Variantshttp://en.wikipedia.org/wiki/ATXhttp://en.wikipedia.org/wiki/As_of_2007http://en.wikipedia.org/wiki/EATX


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standard ATX motherboard. The mounting hole pattern for the upper portion of

the board matches ATX.

ETX - used in embedded systems andsingle board computers.

microATX - a smaller variant of the ATX form factor (about 25% shorter). It is

compatible with most ATX cases, but supports fewer expansion slots due to its

smaller size. Very popular for desktop and small form factorcomputersas of

2007.

FlexATX - a subset of microATX developed by Intel in 1999. Allows more

flexible motherboard design, component positioning and shape.

LPX - based on a design by Western Digital, it allowed smaller cases than the AT

standard, by putting the expansion card slots on a riser(image). LPX was never

standardized and generally only used by large OEMs.

NLX - a low-profile design released in 1997. It also incorporated a riser for

expansion cards, and never became popular.

BTX (Balanced Technology Extended) - a standard proposed by Intel as a

successor to ATX in the early 2000s.

Mini-ITX - a small, highly-integrated form factor created by VIA in 2001. Mini-

ITX was designed for small devices such as thin clientsandset-top boxes.

WTX - created by Intel in 1998. A large design for servers and high-end

workstations featuring multiple CPUs and hard drives.

Laptop computers generally use highly integrated, miniaturized, and customized

motherboards. This is one of the reasons that laptop computers are difficult to upgrade

and expensive to repair. Often the failure of one laptop component requires the

replacement of the entire motherboard, which is usually more expensive than a desktop

motherboard due to the large number of integrated components.

Visual comparison

This image compares the sizes of common form factors to ISO 216paper sizes (e.g.A4):
http://en.wikipedia.org/wiki/ETX_Form_Factorhttp://en.wikipedia.org/wiki/Embedded_systemhttp://en.wikipedia.org/wiki/Single_board_computerhttp://en.wikipedia.org/wiki/Single_board_computerhttp://en.wikipedia.org/wiki/Single_board_computerhttp://en.wikipedia.org/wiki/MicroATXhttp://en.wikipedia.org/wiki/Small_form_factorhttp://en.wikipedia.org/wiki/As_of_2007http://en.wikipedia.org/wiki/As_of_2007http://en.wikipedia.org/wiki/As_of_2007http://en.wikipedia.org/wiki/FlexATXhttp://en.wikipedia.org/wiki/LPX_form_factorhttp://en.wikipedia.org/wiki/Western_Digitalhttp://en.wikipedia.org/wiki/Riserhttp://en.wikipedia.org/wiki/Riserhttp://www.motherboards.org/images/articles/tech-planations/nlxphoto.gifhttp://en.wikipedia.org/wiki/Original_equipment_manufacturerhttp://en.wikipedia.org/wiki/Original_equipment_manufacturerhttp://en.wikipedia.org/wiki/NLXhttp://en.wikipedia.org/wiki/BTX_(form_factor)http://en.wikipedia.org/wiki/Mini-ITXhttp://en.wikipedia.org/wiki/VIA_Technologieshttp://en.wikipedia.org/wiki/Thin_clienthttp://en.wikipedia.org/wiki/Thin_clienthttp://en.wikipedia.org/wiki/Set-top_boxhttp://en.wikipedia.org/wiki/Set-top_boxhttp://en.wikipedia.org/wiki/Set-top_boxhttp://en.wikipedia.org/wiki/WTXhttp://en.wikipedia.org/wiki/CPUhttp://en.wikipedia.org/wiki/Hard_drivehttp://en.wikipedia.org/wiki/Laptophttp://en.wikipedia.org/wiki/ISO_216http://en.wikipedia.org/wiki/ISO_216http://en.wikipedia.org/wiki/Paper_sizehttp://en.wikipedia.org/wiki/Paper_sizehttp://en.wikipedia.org/wiki/ETX_Form_Factorhttp://en.wikipedia.org/wiki/Embedded_systemhttp://en.wikipedia.org/wiki/Single_board_computerhttp://en.wikipedia.org/wiki/MicroATXhttp://en.wikipedia.org/wiki/Small_form_factorhttp://en.wikipedia.org/wiki/As_of_2007http://en.wikipedia.org/wiki/As_of_2007http://en.wikipedia.org/wiki/FlexATXhttp://en.wikipedia.org/wiki/LPX_form_factorhttp://en.wikipedia.org/wiki/Western_Digitalhttp://en.wikipedia.org/wiki/Riserhttp://www.motherboards.org/images/articles/tech-planations/nlxphoto.gifhttp://en.wikipedia.org/wiki/Original_equipment_manufacturerhttp://en.wikipedia.org/wiki/NLXhttp://en.wikipedia.org/wiki/BTX_(form_factor)http://en.wikipedia.org/wiki/Mini-ITXhttp://en.wikipedia.org/wiki/VIA_Technologieshttp://en.wikipedia.org/wiki/Thin_clienthttp://en.wikipedia.org/wiki/Set-top_boxhttp://en.wikipedia.org/wiki/WTXhttp://en.wikipedia.org/wiki/CPUhttp://en.wikipedia.org/wiki/Hard_drivehttp://en.wikipedia.org/wiki/Laptophttp://en.wikipedia.org/wiki/ISO_216http://en.wikipedia.org/wiki/Paper_size


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http://en.wikipedia.org/wiki/Image:Motherboards_form_factors.svg


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Hard disk drive

A hard disk drive (HDD), commonly referred to as a hard drive orhard disk,[1] is anon-volatile storage device which stores digitally encoded data on rapidly rotatingplatterswith magnetic surfaces. Strictly speaking, "drive" refers to a device distinct from

its medium, such as a tape drive and its tape, or a floppy disk drive and its floppy disk.Early HDDs had removable media; however, an HDD today is typically a sealed unitwith fixed media.[2]

HDDs were originally developed for use with computers. In the 21st century, applicationsfor HDDs have expanded beyond computers to include digital video recorders,digitalaudio players,personal digital assistants, digital cameras, and video game consoles. In2005 the first mobile phonesto include HDDs were introduced by SamsungandNokia.The need for large-scale, reliable storage, independent of a particular device, led to theintroduction of configurations such as RAIDarrays,network attached storage (NAS)systems and storage area network(SAN) systems that provide efficient and reliable

access to large volumes of data.

Contents

1 Technology 2 Capacity and access speed

o 2.1 Capacity measurements

3 History 4 Hard disk drive characteristics 5 Integrity

o

5.1 Landing zones 6 Access and interfaces

o 6.1 Disk families used in personal computers

7 Manufacturers 8 See also 9 Notes & references

10 External links
http://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#_note-0#_note-0http://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#_note-0#_note-0http://en.wikipedia.org/wiki/Non-volatile_storagehttp://en.wikipedia.org/wiki/Hard_disk_plattershttp://en.wikipedia.org/wiki/Hard_disk_plattershttp://en.wikipedia.org/wiki/Magnetichttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#_note-1#_note-1http://en.wikipedia.org/wiki/Computerhttp://en.wikipedia.org/wiki/Computerhttp://en.wikipedia.org/wiki/Digital_video_recorderhttp://en.wikipedia.org/wiki/Digital_video_recorderhttp://en.wikipedia.org/wiki/Digital_audio_playerhttp://en.wikipedia.org/wiki/Digital_audio_playerhttp://en.wikipedia.org/wiki/Digital_audio_playerhttp://en.wikipedia.org/wiki/Personal_digital_assistanthttp://en.wikipedia.org/wiki/Digital_camerahttp://en.wikipedia.org/wiki/Video_game_consolehttp://en.wikipedia.org/wiki/Video_game_consolehttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Samsung_Electronicshttp://en.wikipedia.org/wiki/Samsung_Electronicshttp://en.wikipedia.org/wiki/Nokiahttp://en.wikipedia.org/wiki/Nokiahttp://en.wikipedia.org/wiki/Redundant_array_of_independent_diskshttp://en.wikipedia.org/wiki/Redundant_array_of_independent_diskshttp://en.wikipedia.org/wiki/Network_attached_storagehttp://en.wikipedia.org/wiki/Network_attached_storagehttp://en.wikipedia.org/wiki/Storage_area_networkhttp://en.wikipedia.org/wiki/Storage_area_networkhttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Technology#Technologyhttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Capacity_and_access_speed#Capacity_and_access_speedhttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Capacity_measurements#Capacity_measurementshttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#History#Historyhttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Hard_disk_drive_characteristics#Hard_disk_drive_characteristicshttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Integrity#Integrityhttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Landing_zones#Landing_zoneshttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Access_and_interfaces#Access_and_interfaceshttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Disk_families_used_in_personal_computers#Disk_families_used_in_personal_computershttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Manufacturers#Manufacturershttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#See_also#See_alsohttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Notes_.26_references#Notes_.26_referenceshttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#External_links#External_linkshttp://en.wikipedia.org/wiki/Image:Hard_disk_platter_reflection.jpghttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#_note-0#_note-0http://en.wikipedia.org/wiki/Non-volatile_storagehttp://en.wikipedia.org/wiki/Hard_disk_plattershttp://en.wikipedia.org/wiki/Magnetichttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#_note-1#_note-1http://en.wikipedia.org/wiki/Computerhttp://en.wikipedia.org/wiki/Digital_video_recorderhttp://en.wikipedia.org/wiki/Digital_audio_playerhttp://en.wikipedia.org/wiki/Digital_audio_playerhttp://en.wikipedia.org/wiki/Personal_digital_assistanthttp://en.wikipedia.org/wiki/Digital_camerahttp://en.wikipedia.org/wiki/Video_game_consolehttp://en.wikipedia.org/wiki/Mobile_phonehttp://en.wikipedia.org/wiki/Samsung_Electronicshttp://en.wikipedia.org/wiki/Nokiahttp://en.wikipedia.org/wiki/Redundant_array_of_independent_diskshttp://en.wikipedia.org/wiki/Network_attached_storagehttp://en.wikipedia.org/wiki/Storage_area_networkhttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Technology#Technologyhttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Capacity_and_access_speed#Capacity_and_access_speedhttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Capacity_measurements#Capacity_measurementshttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#History#Historyhttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Hard_disk_drive_characteristics#Hard_disk_drive_characteristicshttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Integrity#Integrityhttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Landing_zones#Landing_zoneshttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Access_and_interfaces#Access_and_interfaceshttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Disk_families_used_in_personal_computers#Disk_families_used_in_personal_computershttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Manufacturers#Manufacturershttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#See_also#See_alsohttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#Notes_.26_references#Notes_.26_referenceshttp://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#External_links#External_links


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Technology

A hard disk drive stores information on one or more rigid, flat circular disks. The disks

are mounted on a spindle, with spacers in between, and a motor on the bottom end of thespindle. To read and write to the surface of the disks, the drive uses a small electro-magnet assembly, referred to as a head, located on the end of an actuator arm. With onehead for each platter surface on the spindle. The disks are spun at a very high speed toallow the head to move quickly over the surface of the disk. Towards the other end of theactuator arm is a pivot point, and at the end is a voice coil, which moves the head. Aboveand below each voice coil is a rare earth magnet. This allows the head to move towardsthe center of the disk or towards the outside, in a radial pattern.

A cross section of the magnetic surface in action. In this case the binary data encodedusing frequency modulation.

The disk controller uses a digital-to-analog converterto control the flow of electricitythrough the voice coil(s) located on the of the actuator arm. Thevoice coil acts as anelectromagnet; it produces a magnetic field that interacts with magnetic fields of themagnet located above and below the voice coil, which causes the voice coil to move theactuator arm, and in turn the head located on the opposite end of the actuator arm. So as

the voice coil is pushed towards one end, the assembly moves the head towards thecenter, and when the voice coil is pushed towards the other end, the heads move towardsthe outside edge of the disk, or the heads are parked. The digital-to-analog converterallows the disk controller to move the head in tiny steps in either direction.

The disks are made of a non-magnetic material, usually aluminum or glass, and arecoated with a very thin layer of magnetic material. Older disks used iron(III) oxideas themagnetic material, but current disks use acobalt-based alloy.
http://en.wikipedia.org/wiki/Rare_earth_magnethttp://en.wikipedia.org/wiki/Frequency_modulationhttp://en.wikipedia.org/wiki/Digital-to-analog_converterhttp://en.wikipedia.org/wiki/Voice_coilhttp://en.wikipedia.org/wiki/Voice_coilhttp://en.wikipedia.org/wiki/Voice_coilhttp://en.wikipedia.org/wiki/Electromagnethttp://en.wikipedia.org/wiki/Iron(III)_oxidehttp://en.wikipedia.org/wiki/Iron(III)_oxidehttp://en.wikipedia.org/wiki/Cobalthttp://en.wikipedia.org/wiki/Cobalthttp://en.wikipedia.org/wiki/Image:MagneticMedia.pnghttp://en.wikipedia.org/wiki/Image:MagneticMedia.pnghttp://en.wikipedia.org/wiki/Image:Hard_drive.svghttp://en.wikipedia.org/wiki/Rare_earth_magnethttp://en.wikipedia.org/wiki/Frequency_modulationhttp://en.wikipedia.org/wiki/Digital-to-analog_converterhttp://en.wikipedia.org/wiki/Voice_coilhttp://en.wikipedia.org/wiki/Voice_coilhttp://en.wikipedia.org/wiki/Electromagnethttp://en.wikipedia.org/wiki/Iron(III)_oxidehttp://en.wikipedia.org/wiki/Cobalt


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The inside of a hard disk drive with the disk(s) and spindle motor hub removed. To theleft of center is the actuator arm. A read-write head is at the end of the arm. The headslider is located just behind the head, on the underside of the arm. The orange wires onthe side of the arm, connect the heads to the drives controller. The pivot point is theround bolt seen just before the metal plate. The semi-circular metal plate, top left corner,is one of the permanent magnets that are used in moving the arm. The voice coil islocated underneath, with a second magnet below.The air filter is within the plastichousing in the bottom left.

The magnetic surface of each platter is divided into many small sub-micrometre-sizedmagnetic regions, each of which is used to encode a single binary unit of information. Intoday's HDDs each of these magnetic regions is composed of a few hundred magneticgrains. Each magnetic region forms a magnetic dipolewhich generates a highly localizedmagnetic field nearby. The write head magnetizes a magnetic region by generating astrong local magnetic field nearby. Early HDDs used the same inductor that was used toread the data as an electromagnet to create this field. Later versions of inductive headsincluded, metal in Gap (MIG) heads and thin film heads. In today's heads the read andwrite elements are separate but are in close proximity on the head portion of an actuatorarm. The read element is typically magneto-resistive while the write element is typicallythin-film inductive[3].

Hard disk drives are sealed to prevent dustand other sources of contamination, frominterfering with the operation of the hard disks heads. The hard drives are not air tight,but rather utilize an extremely fine air filter, to allow for air inside the hard driveenclosure. The spinning of the disks causes the air to circulate forcing any particulates tobecome trapped on the filter. The spinning of the disks, also allows the hard disk heads tofloat above the surface of the disk surface using the same air currents. See Bernoulli'sprinciple.

Using rigid disks and sealing the unit allows much tighter tolerances than in a floppy diskdrive. Consequently, hard disk drives can store much more data than floppy disk drives

and access and transmit it faster. In 2007, a typical enterprise, i.e. workstation HDDmight store between 160 GB and 1 TB of data (as of local US market by July 2007),rotate at 7,200 or 10,000 revolutions per minute (RPM), and have a sequential mediatransfer rate of over 80 MB/s. The fastest enterprise HDDs spin at 15,000 RPM, and canachieve sequential media transfer speeds up to and beyond 110 MB/s.[4] Mobile, i.e.,Laptop HDDs, which are physically smaller than their desktop and enterprisecounterparts, tend to be slower and have less capacity. In the 1990s, most spun at 4,200
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RPM[5]. In 2007, a typical mobile HDD spins at 5,400 RPM, with 7,200 RPM modelsavailable for a slight price premium.

Capacity and access speed

PC hard disk drive capacity (in GB). The plot is logarithmic, so the fit line corresponds toexponential growth.

The exponential increases in disk space and data access speeds of HDDs have enabled thecommercial viability of consumer products that require large storage capacities, such asthe Apple iPoddigital music playerand the TiVopersonal video recorder.[6] In addition,the availability of vast amounts of cheap storage has made viable a variety of web-basedsystems with extraordinary capacity requirements, such as the search and email systemsoffered by companies like Google.

The main way to decrease access time is to increase rotational speed, while the main wayto increase throughput and storage capacity is to increase areal density. A vice presidentofSeagate Technology projects a future growth in disk density of 40% per year.[7]Access

times have not kept up with throughput increases, which themselves have not kept upwith growth in storage capacity.

As of2006, disk drives includeperpendicular recording technology, in the attempt toenhance recording density and throughput.[8]

The first 3.5" HDD marketed as able to store 1 TB is the Hitachi Deskstar7K1000. Thedrive contains five platters at approximately 200 GB each, providing 935.5 GiB of usablespace.[9] Hitachi has since been joined by Samsung and Seagate in the 1 TB drive market.[10]

Standard Name Width Largest capacity to date (2007) Platters (Max)5.25" FH 146 mm 47GB[11] 14

5.25" HH 146 mm 19.3GB[12] 4[13]

3.5" 102 mm 1.2TB 5

2.5" 69.9 mm 250 GB [14] 3

1.8" (PCMCIA) 54 mm 100 GB [15]

1.8" (ATA-7 LIF) 53.8 mm
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Capacity measurements

The capacity of an HDD can be calculated by multiplying the number of cylinders by thenumber of heads by the number of sectors by the number of bytes/sector (most commonly512). On ATAdrives bigger than 8 gigabytes, the values are set to 16383 cylinder, 16

heads, 63 sectors for compatibility with older operating systems. It should be noted thatthe values for cylinder, head & sector reported by a modern drive are not the actualphysical parameters since, amongst other things, with zone bit recording the number ofsectors varies by zone.

Hard disk drive manufacturers specify disk capacity using theSI prefixesmega,giga, andtera and their abbreviations M, G and T, respectively. Byte is typically abbreviated B.

Operating systems frequently report capacity using the same abbreviations but with abinary interpretation. For instance, the prefixmega can also mean 220 (1,048,576), whichis approximately 1,000,000. Similar usage has been applied to prefixes of greater

magnitude. This results in a discrepancy between the disk manufacturer's stated capacityand what the system reports. The difference becomes much more noticeable in the multi-gigabyte range. For example, Microsoft Windows reports disk capacity both in decimal to12 or more significant digits and with binary prefixes to 3 significant digits. Thus a diskspecified by a disk manufacturer as a 30 GB disk might have its capacity reported byWindows 2000 both as "30,065,098,568 bytes" and "28.0 GB" The disk manufacturerused the SI definition of "giga", 109 to arrive at 30 GB; however, because the utilitiesprovided by Windows define a gigabyte as 1,073,741,824 bytes (230 bytes), the operatingsystem reports capacity of the disk drive as 28.0 GB.
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History

Main article:History of hard disk drives

IBM 62PC "Piccolo" HDD, circa 1979 - an early 8" disk

For many years, HDDs were large, cumbersome devices, more suited to use in the

protected environment of a data center or large office than in a harsh industrialenvironment (due to their delicacy), or small office or home (due to their size and powerconsumption). Before the early 1980s, most HDDs had 8-inch (20 cm) or 14-inch (35 cm)platters, required an equipment rack or a large amount of floor space (especially the largeremovable-media disks, which were often referred to as "washing machines"), and inmany cases needed high-current or even three-phase power hookups due to the largemotors they used. Because of this, HDDs were not commonly used with microcomputersuntil after 1980, when Seagate Technology introduced the ST-506, the first 5.25-inchHDD, with a capacity of 5 megabytes. In fact, in its factory configuration, the originalIBM PC (IBM 5150) was not equipped with a hard disk drive.

Most microcomputer HDDs in the early 1980s were not sold under their manufacturer'snames, but by OEMs as part of larger peripherals (such as the Corvus Disk System andthe Apple ProFile). The IBM PC/XT had an internal HDD, however, and this started atrend toward buying "bare" disks (often by mail order) and installing them directly into asystem. Hard disk drive makers started marketing to end users as well as OEMs, and bythe mid-1990s, HDDs had become available on retail store shelves.

While internal disks became the system of choice on PCs, external HDDs remainedpopular for much longer on the Apple Macintosh and other platforms. The first AppleMacintosh built between 1984 and 1986 had a closed architecture that did not support anexternal or internal hard drive. In 1986, Apple added aSCSI port on the back, makingexternal expansion easy. External SCSI drives were also popular with oldermicrocomputers such as theApple II series, and were also used extensively in servers, ausage which is still popular today. The appearance in the late 1990s of high-speedexternal interfaces such as USB and FireWirehas made external disk systems popularamong PC users once again, especially for laptop users, users that install Linux in theadditional external unit and users who move large amounts of data between two or moreareas. Most HDD makers now make their disks available in external cases.
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Hard disk drive characteristics

5.25" MFM 110 MB HDD (2.5" ATA 6495 MB HDD, US & UK pennies forcomparison)

Capacity of a hard disk drive is usually quoted ingigabytes. Older HDDs quoted theirsmaller capacities in megabytes.

The data transfer rate at the inner zone ranges from 44.2MB/s to 74.5 MB/s, while thetransfer rate at the outer zone ranges from 74.0 MB/s to 111.4 MB/s. An HDD's randomaccess time ranges from 5ms to 15 ms.

The physical size of a hard disk drive is quoted ininches. The majority of HDDs used indesktops today are 3.5" wide, while those used in laptops are 2.5" wide. As of early 2007,manufacturers have started selling SATA and SAS 2.5 inch drives for use in servers anddesktops.

An increasingly common form factor is the 1.8" ATA-7 LIF form factor used insidedigital audio players and subnotebooks, which provide up to 100GB storage capacity atlow power consumption and are highly shock-resistant. A previous 1.8" HDD standardexists, for 25GB sized disks that fit directly into aPC card expansion slot. From these,the smaller 1" form factor was evolved, which is designed to fit the dimensions ofCFType II, which is also usually used as storage for portable devices including digitalcameras. 1" was a de facto form factor led byIBM's Microdrive, but is now genericallycalled 1" due to other manufacturers producing similar products. There is also a 0.85 inchform factor produced by Toshiba for use in mobile phones and similar applications,includingSD/MMC slot compatible HDDs optimized for video storage on 4G handsets.

The size designations are more nomenclature than descriptive. The names refer to thewidth of the disk inserted into the drive rather than the actual width of the entire drive. A5.25" drive has an actual width of 5.75", a 3.5" drive 4", a 2.5" drive 2.75". A 1.8" drivecan have different widths, depending on its form factor. A PCMCIA drive has a width of54 mm, while an ATA-7 LIF form factor drive has a width of 2.12".
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A hard disk is defined to be at "full height" if its height is 3.25". It is "half height" at aheight of 1.625". A "slim height" or "low profile" HDD has a height of 1". "Ultra lowprofile" drives can have heights of 0.75", 0.67", 0.49" or 0.37".

Integrity

An IBM HDD head suspended above the disk platter.

The HDD's spindle system relies on air pressure inside the enclosure to support the headsat their properflying heightwhile the disk rotates. An HDD requires a certain range of airpressures in order to operate properly. The connection to the external environment andpressure occurs through a small hole in the enclosure (about 0.5 mm in diameter), usuallywith a carbon filter on the inside (the breather filter, see below). If the air pressure is toolow, then there is not enough lift for the flying head, so the head gets too close to thedisk, and there is a risk of head crashes and data loss. Specially manufactured sealed andpressurized disks are needed for reliable high-altitude operation, above about 10,000 feet(3,000 m). This does not apply to pressurized enclosures, like anairplanepressurizedcabin. Modern disks include temperature sensors and adjust their operation to theoperating environment.

Very high humidity for extended periods can corrode the heads and platters. If the diskuses "Contact Start/Stop" (CSS) technology to park its heads on the platters when notoperating, increased humidity can also lead to increasedstiction (the tendency for theheads to stick to the platter surface). This can cause physical damage to the platter andspindle motor and cause head crash. Breather holes can be seen on all disks theyusually have a sticker next to them, warning the user not to cover the holes. The air insidethe operating disk is constantly moving too, being swept in motion by friction with thespinning platters. This air passes through an internal recirculation (or "recirc") filter toremove any leftover contaminants from manufacture, any particles or chemicals that mayhave somehow entered the enclosure, and any particles or outgassing generated internallyin normal operation.
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Close-up of a hard disk head suspended above the disk platter together with its mirrorimage in the smooth surface of the magnetic platter.

Due to the extremely close spacing between the heads and the disk surface, anycontamination of the read-write heads or platters can lead to ahead crash a failure ofthe disk in which the head scrapes across the platter surface, often grinding away the thinmagnetic film. Forgiant magnetoresistive (GMR) heads in particular, a minor head crash

from contamination (that does not remove the magnetic surface of the disk) still results inthe head temporarily overheating, due to friction with the disk surface, and can render thedata unreadable for a short period until the head temperature stabilizes (so called "thermalasperity," a problem which can partially be dealt with by proper electronic filtering of theread signal). Head crashes can be caused by electronic failure, a sudden power failure,physical shock, wear and tear, corrosion, or poorly manufactured platters and heads. Inmost desktop and server disks, when powering down, the heads are moved to a landingzone, an area of the platter usually near its inner diameter (ID), where no data are stored.This area is called the CSS (Contact Start/Stop) zone. However, especially in old models,sudden power interruptions or a power supply failure can sometimes result in the deviceshutting down with the heads in the data zone, which increases the risk of data loss. In

fact, it used to be procedure to "park" the hard disk before shutting down your computer.Newer disks are designed such that either a spring (at first) or (more recently) rotationalinertia in the platters is used to safely park the heads in the case of unexpected powerloss.

The hard disk's electronics control the movement of the actuator and the rotation of thedisk, and perform reads and writes on demand from the disk controller. Modern diskfirmware is capable of scheduling reads and writes efficiently on the platter surfaces andremapping sectors of the media which have failed. Also, most major hard disk andmotherboard vendors now support self-monitoring, analysis, and reporting technology(S.M.A.R.T.), which attempt to alert users to impending failures.

However, not all failures are predictable. Normal use eventually can lead to a breakdownin the inherently fragile device, which makes it essential for the user to periodically backup the data onto a separate storage device. Failure to do so can lead to the loss of data.While it may be possible to recover lost information, it is normally an extremely costlyprocedure, and it is not possible to guarantee success in the attempt. A 2007 studypublished by Google suggested very little correlation between failure rates and eitherhigh temperature or activity level.[16] While several S.M.A.R.T. parameters have an
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impact on failure probability, a large fraction of failed drives do not produce predictiveS.M.A.R.T. parameters.[16] S.M.A.R.T. parameters alone may not be useful for predictingindividual drive failures.[16]

Landing zones

Microphotograph of a hard disk head. The size of the front face (which is the "trailingface" of the slider) is about 0.3 mm 1.0 mm. The (not visible) bottom face of the slideris about 1.0 mm 1.25 mm (so called "nano" size) and faces the platter. One functionalpart of the head is the round, orange structure in the middle - the lithographicallydefinedcopper coil of the write transducer. Also note the electric connections by wires bonded togold-plated pads.

Spring tension from the head mounting constantly pushes the heads towards the platter.

While the disk is spinning, the heads are supported by an air bearing and experience nophysical contact or wear. In CSS drives the sliders carrying the head sensors (often alsojust called heads) are designed to reliably survive a number of landings and takeoffs fromthe media surface, though wear and tear on these microscopic components eventuallytakes its toll. The heads typically land in a "landing zone" that does not contain user data.Most manufacturers design the sliders to survive 50,000 contact cycles before the chanceof damage on startup rises above 50%. However, the decay rate is not linearwhen adisk is younger and has fewer start-stop cycles, it has a better chance of surviving thenext startup than an older, higher-mileage disk (as the head literally drags along the disk'ssurface until the air bearing is established). For example, the Seagate Barracuda 7200.10series of desktop hard disks are rated to 50,000 start-stop cycles. [17] This means that no

failures attributed to the head-platter interface were seen before at least 50,000 start-stopcycles during testing.

Around 1995 IBM pioneered a technology where a landing zone on the disk is made by aprecision laser process (Laser Zone Texture = LZT) producing an array of smoothnanometer-scale "bumps" in a landing zone, thus vastly improving stiction and wearperformance. This technology is still largely in use today (2006). In most mobileapplications, the heads are lifted off the platters onto plastic "ramps" near the outer disk
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edge, thus eliminating the risks of wear and stiction altogether and greatly improvingnon-operating shock performance. All HDDs use one of these two technologies. Each hasa list of advantages and drawbacks in terms of loss of storage space, relative difficulty ofmechanical tolerance control, cost of implementation, etc.

IBM created a technology for theirThinkpad line of laptop computers called the ActiveProtection System. When a sudden, sharp movement is detected by the built-in motionsensor in the Thinkpad, internal hard disk heads automatically unload themselves into theparking zone to reduce the risk of any potential data loss or scratches made. Apple lateralso utilized this technology in their Powerbook, iBook, MacBook Pro, and MacBookline, known as the Sudden Motion Sensor.Toshiba has released similar technology intheir laptops.[18]

Access and interfaces

Hard disk drives are accessed over one of a number of bus types, including ATA (IDE,

EIDE), Serial ATA (SATA), SCSI, SAS, and Fibre Channel. Bridge circuitry issometimes used to connect hard disk drives to busses that they cannot communicate withnatively, such as IEEE 1394 and USB.

Back in the days of the ST-506interface, the data encoding scheme was also important.The first ST-506 disks used Modified Frequency Modulation (MFM) encoding, andtransferred data at a rate of 5 megabitsper second. Later on, controllers using 2,7RLL(orjust "RLL") encoding increased the transfer rate by fifty percent, to 7.5 megabits persecond; it also increased disk capacity by fifty percent.

Many ST-506 interface disk drives were only specified by the manufacturer to run at the

lower MFM data rate, while other models (usually more expensive versions of the samebasic disk drive) were specified to run at the higher RLL data rate. In some cases, a diskdrive had sufficient margin to allow the MFM specified model to run at the faster RLLdata rate; however, this was often unreliable and was not recommended. (An RLL-certified disk drive could run on a MFM controller, but with 1/3 less data capacity andspeed.)

Enhanced Small Disk Interface (ESDI) also supported multiple data rates (ESDI disksalways used 2,7 RLL, but at 10, 15 or 20 megabits per second), but this was usuallynegotiated automatically by the disk drive and controller; most of the time, however, 15or 20 megabit ESDI disk drives weren't downward compatible (i.e. a 15 or 20 megabit

disk drive wouldn't run on a 10 megabit controller). ESDI disk drives typically also hadjumpers to set the number of sectors per track and (in some cases) sector size.

SCSI originally had just one speed, 5 MHz (for a maximum data rate of 5 megabytes persecond), but later this was increased dramatically. The SCSI bus speed had no bearing onthe disk's internal speed because of buffering between the SCSI bus and the disk drive'sinternal data bus; however, many early disk drives had very small buffers, and thus had to
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be reformatted to a different interleave (just like ST-506 disks) when used on slowcomputers, such as early IBM PC compatiblesand earlyApple Macintoshes.

ATA disks have typically had no problems with interleave or data rate, due to theircontroller design, but many early models were incompatible with each other and couldn't

run in a master/slave setup (two disks on the same cable). This was mostly remedied bythe mid-1990s, when ATA's specification was standardised and the details began to becleaned up, but still causes problems occasionally (especially with CD-ROM and DVD-ROM disks, and when mixing Ultra DMA and non-UDMA devices).

Serial ATA does away with master/slave setups entirely, placing each disk on its ownchannel (with its own set of I/O ports) instead.

FireWire/IEEE 1394 and USB(1.0/2.0) HDDs are external units containing generallyATA or SCSI disks with ports on the back allowing very simple and effective expansionand mobility. Most FireWire/IEEE 1394 models are able to daisy-chainin order to

continue adding peripherals without requiring additional ports on the computer itself.

Disk families used in personal computers

Notable disk families include:

Bit Serial Interfaces These families connected to a hard disk drive controllerwith three cables, one for data, one for control and one for power. The HDDcontroller provided significant functions such as serial to parallel conversion, dataseparation and track formatting, and required matching to the drive in order toassure reliability.

o ST506 used MFM (Modified Frequency Modulation) for the dataencoding method.

o ST412 was available in either MFM orRLL(Run Length Limited)

variants.o ESDI (Enhanced Small Disk Interface) was an interface developed by

Maxtor to allow faster communication between the PC and the disk thanMFM or RLL.

Word Serial Interfaces These families connect to a host bus adapter (todaytypically integrated into the "South Bridge") with two cables, one for data/controland one for power. The earliest versions of these interfaces typically had a 16 bitparallel data transfer to/from the drive and there are 8 and 32 bit variants. Modern

versions have serial data transfer. The word nature of data transfer makes thedesign of a host bus adapter significantly simpler than that of the precursor HDDcontroller.

o Integrated Drive Electronics (IDE) was later renamed to ATA, and then

later, PATA ("parallel ATA", to distinguish it from the new serial ATAinterface, SATA). The name comes from the way early families had theHDD controller external to the disk. Moving the HDD controller from theinterface card to the disk helped to standardize interfaces, including
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reducing the cost and complexity. The 40 pin IDE/ATA connection ofPATA transfers 16 bits of data at a time on the data cable. The data cablewas originally 40 conductor, but later higher speed requirements for datatransfer to and from the hard drive led to an "ultra DMA" mode, known asUDMA, which required an 80 conductor variant of the same cable; the

other conductors provided the grounding necessary for enhanced high-speed signal quality. The interface for 80 pin only has 39 pins, the missingpin acting as a key to prevent incorrect insertion of the connector to anincompatible socket, a common cause of disk and controller damage.

o EIDE was an unofficial update (by Western Digital) to the original IDE

standard, with the key improvement being the use ofDMA("Directmemory access") to transfer data between the disk and the computerwithout the involvement of the CPU, an improvement later adopted by theofficial ATA standards. By directly transferring data between memory anddisk, DMA does not require the CPU/program/operating system to leaveother tasks idle while the data transfer occurs.

o

SCSI (Small Computer System Interface) was an early competitor withESDI, originally named SASI for Shugart Associates. SCSI disks werestandard on servers, workstations, and Apple Macintoshcomputersthrough the mid-90s, by which time most models had been transitioned toIDE (and later, SATA) family disks. Only in 2005 did the capacity ofSCSI disks fall behind IDE disk technology, though the highest-performance disks are still available in SCSI and Fibre Channel only. Thelength limitations of the data cable allows for external SCSI devices.Originally SCSI data cables used single ended data transmission, butserver class SCSI could use differential transmission, and thenFibreChannel (FC) interface, and then more specifically the Fibre Channel

Arbitrated Loop (FC-AL), connected SCSI HDDs using fibre optics. FC-AL is the cornerstone ofstorage area networks, although other protocolslike iSCSI and ATA over Ethernet have been developed as well.

o SATA (Serial ATA). The SATA data cable has one data pair for

differential transmission of data to the device, and one pair for differentialreceiving from the device, just like EIA-422. That requires that data betransmitted serially. The samedifferential signaling system is used inRS485, LocalTalk, USB,Firewire, and differential SCSI.

o SAS (Serial Attached SCSI). The SAS is a new generation serial

communication protocol for devices designed to allow for much higherspeed data transfers and is compatible with SATA. SAS uses serial

communication instead of the parallel method found in traditional SCSIdevices but still uses SCSI commands for interacting with SAS

Acronym Meaning Description

SASIShugart AssociatesSystem Interface

Predecessor to SCSI

SCSISmall ComputerSystem Interface

Bus oriented that handles concurrent operations.
http://en.wikipedia.org/wiki/Ground_(electricity)http://en.wikipedia.org/wiki/Direct_memory_accesshttp://en.wikipedia.org/wiki/Direct_memory_accesshttp://en.wikipedia.org/wiki/CPUhttp://en.wikipedia.org/wiki/CPUhttp://en.wikipedia.org/wiki/SCSIhttp://en.wikipedia.org/wiki/Apple_Macintoshhttp://en.wikipedia.org/wiki/Apple_Macintoshhttp://en.wikipedia.org/wiki/Fibre_Channelhttp://en.wikipedia.org/wiki/Fibre_Channelhttp://en.wikipedia.org/wiki/Fibre_Channelhttp://en.wikipedia.org/wiki/Arbitrated_loophttp://en.wikipedia.org/wiki/Arbitrated_loophttp://en.wikipedia.org/wiki/Storage_area_networkhttp://en.wikipedia.org/wiki/Storage_area_networkhttp://en.wikipedia.org/wiki/ISCSIhttp://en.wikipedia.org/wiki/ATA_over_Ethernethttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/EIA-422http://en.wikipedia.org/wiki/EIA-422http://en.wikipedia.org/wiki/Differential_signalinghttp://en.wikipedia.org/wiki/Differential_signalinghttp://en.wikipedia.org/wiki/RS485http://en.wikipedia.org/wiki/LocalTalkhttp://en.wikipedia.org/wiki/USBhttp://en.wikipedia.org/wiki/Firewirehttp://en.wikipedia.org/wiki/Firewirehttp://en.wikipedia.org/wiki/SCSIhttp://en.wikipedia.org/wiki/Serial_Attached_SCSIhttp://en.wikipedia.org/wiki/Acronymhttp://en.wikipedia.org/wiki/SASIhttp://en.wikipedia.org/wiki/SCSIhttp://en.wikipedia.org/wiki/Computer_bushttp://en.wikipedia.org/wiki/Concurrenthttp://en.wikipedia.org/wiki/Ground_(electricity)http://en.wikipedia.org/wiki/Direct_memory_accesshttp://en.wikipedia.org/wiki/CPUhttp://en.wikipedia.org/wiki/SCSIhttp://en.wikipedia.org/wiki/Apple_Macintoshhttp://en.wikipedia.org/wiki/Fibre_Channelhttp://en.wikipedia.org/wiki/Fibre_Channelhttp://en.wikipedia.org/wiki/Arbitrated_loophttp://en.wikipedia.org/wiki/Arbitrated_loophttp://en.wikipedia.org/wiki/Storage_area_networkhttp://en.wikipedia.org/wiki/ISCSIhttp://en.wikipedia.org/wiki/ATA_over_Ethernethttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/EIA-422http://en.wikipedia.org/wiki/Differential_signalinghttp://en.wikipedia.org/wiki/RS485http://en.wikipedia.org/wiki/LocalTalkhttp://en.wikipedia.org/wiki/USBhttp://en.wikipedia.org/wiki/Firewirehttp://en.wikipedia.org/wiki/SCSIhttp://en.wikipedia.org/wiki/Serial_Attached_SCSIhttp://en.wikipedia.org/wiki/Acronymhttp://en.wikipedia.org/wiki/SASIhttp://en.wikipedia.org/wiki/SCSIhttp://en.wikipedia.org/wiki/Computer_bushttp://en.wikipedia.org/wiki/Concurrent


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SAS Serial Attached SCSI

ATAAdvancedTechnologyAttachment

Successorto ST-412/506/ESDI by integrating the diskcontroller completely onto the device. Incapable ofconcurrent operations.

SATA Serial ATA

ST-506 Seagate interfaceST-412 Seagate interface (minor improvement over ST-506)

ESDIEnhanced SmallDisk Interface

Faster and more integrated than ST-412/506, but stillbackwards compatible

Manufacturers

Seagate3.5 inch 40 GB HDD.

The technological resources and know-how required for modern drive development andproduction mean that as of 2007, over 98% of the world's HDDs are manufactured by justa handful of large firms: Seagate, Western Digital,Samsung, andHitachi (which ownsthe former disk manufacturing division ofIBM).Fujitsu continues to make mobile- and

server-class disks but exited the desktop-class market in 2001. Toshiba is a majormanufacturer of 2.5-inch and 1.8-inch notebook disks. ExcelStoris a small HDDmanufacturer.

Dozens of former HDD manufacturers have gone out of business, merged, or closed theirHDD divisions; as capacities and demand for products increased, profits became hard tofind, and the market underwent significant consolidation in the late 1980s and late 1990s.The first notable casualty of the business in the PC era was Computer Memories Inc. orCMI; after an incident with faulty 20 MB AT disks in 1985,[19] CMI's reputation neverrecovered, and they exited the HDD business in 1987. Another notable failure wasMiniScribe, who went bankrupt in 1990 after it was found that they had engaged in

accounting fraud and inflated sales numbers for several years. Many other smallercompanies (like Kalok, Microscience, LaPine, Areal, Priam and PrairieTek) also did notsurvive the shakeout, and had disappeared by 1993; Micropolis was able to hold on until1997, andJTS, a relative latecomer to the scene, lasted only a few years and was gone by1999, after attempting to manufacture HDDs inIndia. Their claim to fame was creating anew 3" form factor drive for use in laptops. Quantum and Integral also invested in the 3"form factor; but eventually gave up as this form factor failed to catch on.[citation needed]

Rodime was also an important manufacturer during the 1980s, but stopped making disks
http://en.wikipedia.org/wiki/Serial_Attached_SCSIhttp://en.wikipedia.org/wiki/Advanced_Technology_Attachmenthttp://en.wikipedia.org/wiki/Successorhttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/ST-506http://en.wikipedia.org/wiki/ST-412http://en.wikipedia.org/wiki/Enhanced_Small_Disk_Interfacehttp://en.wikipedia.org/wiki/Seagate_Technologyhttp://en.wikipedia.org/wiki/Seagate_Technologyhttp://en.wikipedia.org/wiki/Seagate_Technologyhttp://en.wikipedia.org/wiki/Western_Digitalhttp://en.wikipedia.org/wiki/Western_Digitalhttp://en.wikipedia.org/wiki/Samsunghttp://en.wikipedia.org/wiki/Samsunghttp://en.wikipedia.org/wiki/Hitachi_Ltd.http://en.wikipedia.org/wiki/Hitachi_Ltd.http://en.wikipedia.org/wiki/International_Business_Machineshttp://en.wikipedia.org/wiki/Fujitsuhttp://en.wikipedia.org/wiki/Fujitsuhttp://en.wikipedia.org/wiki/Toshibahttp://en.wikipedia.org/wiki/ExcelStorhttp://en.wikipedia.org/wiki/ExcelStorhttp://en.wikipedia.org/wiki/Consolidationhttp://en.wikipedia.org/wiki/Computer_Memories_Inc.http://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#_note-17#_note-17http://en.wikipedia.org/wiki/MiniScribehttp://en.wikipedia.org/wiki/Kalokhttp://en.wikipedia.org/w/index.php?title=Microscience_International_Corporation&action=edithttp://en.wikipedia.org/w/index.php?title=Microscience_International_Corporation&action=edithttp://en.wikipedia.org/wiki/Micropolis_Corporationhttp://en.wikipedia.org/wiki/JT_Storagehttp://en.wikipedia.org/wiki/JT_Storagehttp://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Wikipedia:Citing_sourceshttp://en.wikipedia.org/wiki/Wikipedia:Citing_sourceshttp://en.wikipedia.org/w/index.php?title=Rodime_plc&action=edithttp://en.wikipedia.org/wiki/Image:Seagate_Hard_Disk.jpghttp://en.wikipedia.org/wiki/Serial_Attached_SCSIhttp://en.wikipedia.org/wiki/Advanced_Technology_Attachmenthttp://en.wikipedia.org/wiki/Successorhttp://en.wikipedia.org/wiki/Serial_ATAhttp://en.wikipedia.org/wiki/ST-506http://en.wikipedia.org/wiki/ST-412http://en.wikipedia.org/wiki/Enhanced_Small_Disk_Interfacehttp://en.wikipedia.org/wiki/Seagate_Technologyhttp://en.wikipedia.org/wiki/Seagate_Technologyhttp://en.wikipedia.org/wiki/Western_Digitalhttp://en.wikipedia.org/wiki/Samsunghttp://en.wikipedia.org/wiki/Hitachi_Ltd.http://en.wikipedia.org/wiki/International_Business_Machineshttp://en.wikipedia.org/wiki/Fujitsuhttp://en.wikipedia.org/wiki/Toshibahttp://en.wikipedia.org/wiki/ExcelStorhttp://en.wikipedia.org/wiki/Consolidationhttp://en.wikipedia.org/wiki/Computer_Memories_Inc.http://f/Komputer/Wikipedia%20English/Harddisk/Harddisk.htm#_note-17#_note-17http://en.wikipedia.org/wiki/MiniScribehttp://en.wikipedia.org/wiki/Kalokhttp://en.wikipedia.org/w/index.php?title=Microscience_International_Corporation&action=edithttp://en.wikipedia.org/wiki/Micropolis_Corporationhttp://en.wikipedia.org/wiki/JT_Storagehttp://en.wikipedia.org/wiki/Indiahttp://en.wikipedia.org/wiki/Wikipedia:Citing_sourceshttp://en.wikipedia.org/w/index.php?title=Rodime_plc&action=edit

Note-Computer and Peripheral

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