4 - Motherboards

8/13/2019 4 - Motherboards

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How Motherboards Workby Gary Brown

BackgroundThe original IBM PC contained the original PC motherboard. In this design, which premieredin 1 !", the motherboard itsel# was a large printed circuit card that contained the !$!!microprocessor , the BI%&, sockets #or the CP'(s )*M and a collection o# slots that au+iliarycards could plug into. I# you wanted to add a #loppy disk dri e or a parallel port or a -oystick ,you bought a separate card and plugged it into one o# the slots. This approach waspioneered in the mass market by the *pple II machine. By making it easy to add cards,

*pple and IBM accomplished two huge things

They made it easy to add new #eatures to the machine o er time.They opened the computer to creati e opportunities #or third/party endors.

0i##erent motherboards o# di##erent intages typically ha e di##erent form factors . The #orm#actor is essentially the si e, shape and design o# the actual motherboard. There are morethan a hal#/do en #orm #actors #or motherboards // check out PC Guide(s Motherboard 2orm2actors to #ind out about the arious designations.

The motherboard, by enabling pluggable components, allows users to personali e acomputer system depending on their applications and needs.

%n the Motherboard * motherboard is a multi/layered printed circuit board . Copper circuit paths called traces that resemble a complicated roadmap carry signals and oltages across the motherboard.3ayered #abrication techni4ues are used so that some layers o# a board can carry data #orthe BI%&, processor and memory buses while other layers carry oltage and ground returnswithout the paths short/circuiting at intersections. The insulated layers are manu#actured intoone complete, comple+ sandwich. Chips and sockets are soldered onto the motherboard. 5+amplesThe M&I 6 70 Pro *) supports dual Pentium microprocessors, has #i e PCI slots and acommunications network riser 8C9): slot. The board supports 1;; M< bus speeds andultra/direct memory access/1$$ 8'0M*:. There are #our '&B ports and onboard audio in the

*T= #orm #actor board.

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The motherboard has been an integral part o# most personal computers #or more than "$ years. Thinko# a motherboard as a scale model o# a #uturistic city with many modular plug/in buildings, each usingpower #rom a common electrical system. Multiple/lane highways o# arious widths transport databetween the buildings. The motherboard is the data and power in#rastructure #or the entire computer.

Motherboards 8also called mainboards : are actually a carryo er #rom architecture used #or years inmain#rame computers . >arious circuit cards per#orming arious #unctions all plug into many similarsockets on a common circuit board. 5ach circuit card per#orms a uni4ue #unction in the computer andgets its power #rom the socket.

0ue to impro ements in circuitry and packaging, motherboards ha e essentially stayed the same si eor shrunk while their #unctionality has skyrocketed. In this edition o# HowStuffWorks , you will learnhow the motherboard operates and what its many sockets and connectors do.
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MSI 694D Pro A Dual !lip "hip Socket #$% motherboard

The *bit ?T/@* supports *d anced Micro 0e ices 8*M0: processors and has the ?T/1;;*chipset. The card slots on the *bit ?T/@*, #rom bottom to top in the image below, shows thatI&* has one slot, PCI has si+ slots and *GP has one slot. * special #an cools the chipset.

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Abit &'($A AMD Processor Motherboard

* partial iew o# the Tech)am &;ProM motherboard shows slots 2rom bottom to top, I&*has one slot, PCI has two slots, audio modem riser 8*M): has one slot, and *GP has oneslot.

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'ech am S#ProM Motherboard

The BI%& chip is common to many motherboards

)I*S "hip

0ata Bus AidthModern Pentium class motherboards ha e a data bus with 67 bits . That is the width o# thedata highway that goes in and out o# the processor. The Pentium processors, howe er, douse ;"/bit registers to handle ;"/bit instructions.

Bus speeds and widths ha e increased due to #aster processors and the needs o#multimedia applications. Typical bus names and widths are

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Industry &tandard *rchitecture 8I&*: / ! or 16 bits 5+tended Industry &tandard *rchitecture 85I&*: / ! or16 bits Microchannel *rchitecture 8MC*: / 16 or ;" bits >5&* 3ocal Bus 8>3B: / ;" bits Peripheral Component Interconnect 8PCI: / ;" or 67 bits *ccelerated Graphics Port 8*GP : / ;" bits

ChipsetsChipsets pro ide the support #or the processor chip on the motherboard. The Intel 77$B= isthe dominant chipset in the non/*pple personal computers . The chipset is the heart o# thecomputer since it controls and determines how #ast and which type o# processor, memory,and slots are used. *nother chip on the motherboard is called the Super I+* controller . Itsmain #unction is to control the #loppy disk dri e , keyboard , mouse , serial and printer ports.Check out PCGuide(s &uper I % Controller 2unctions to learn more.

)ecent motherboard designs include additional chips to support '&B, sound card, ideoadapter, computer host and network adapter. These chips sa e the cost o# an adapter slot.

2ans&peeds , temperatures, density, #aster chipset designs and component count ha e dri en theneed #or circuit cooling ia miniature electric #ans. These #ans mount inside the actualcomputer case. Heat sinks act like a car radiator , pro iding additional sur#ace area to helpcool a component.

)eplaceable #an heat/sink assemblies are o#ten used to help dissipate the considerableamount o# heat on modern processor chips. The assembly conducts heat away #rom the chipby con ection, using a layer o# thermal grease between the two mating metal sur#aces. 2anso#ten ha e a third wire used #or monitoring the speed o# the #an.

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4 - Motherboards