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Computer Hardware

Ministry of Higher EducationBamyan University

Computer Science Department

Presented by : Mustafa Kamel MohammadiEmail : bamian.cs@gmail.com

Buses and Chipsets

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learning objective In this chapter you will learn

What is a chip in motherboard? What chipset controllers are. How all components on the motherboard are connected through buses. Types of buses System buses I/O buses

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Controller chips and chipsets• The motherboard’s busses are regulated by a number of controllers. • These are small circuits which have been designed to look after a particular job.• Most of these controller functions are grouped together into a couple of large

chips, which together comprise the chip set.• The circuits in the chipsets give motherboards intelligence and ability to work• Controls the movement of data, instruction and control signals between CPU,

RAM, Cashe, I/O devices• Contains enough instructions to perform its functions at the very lowest level• The more newer chipsets

• Higher speed• New devices like RAM, Buses and … support

• Plays a major role in systems functions, feature set and speed.

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North bridge and South bridge• The two chip, chipset that contains north bridge chip and south bridge chip• Connects the motherboard buses with each other• The north bridge and south bridge are connected by a powerful bus, which

sometimes is called a link channel.• Share the work of managing the data traffic on the motherboard.

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North bridge• Controller that controls the flow of Data between CPU, RAM and Video ports

(AGP or PCI).• Connects the most high performance devices• May contain more circuitry than other chips• Handle a huge traffic between above components• May have a heat sink to control the heat.

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South bridge• Includes the controller of peripheral devices that are not the essential part of

system.• Physically located close to I/O ports.• Connects devices with lower speed.• Sends data to CPU, RAM through LINK to north bridge.

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Controller chips• A controller is typically a single chip that controls the flow of data to and from

peripheral devices.• Each device added to the PC that wishes to interact with the data bus requires a

controller.• Sometimes it is not possible to include all controllers of devices in a chipset• There are controllers that are directly mounted to motherboard like

• Keyboard controller• I/O controller

• Some expansion cards like the followings have built in controller chips• Sound cards• Video cards• Network interface cards

• Individual controller chips come in various size and shapes

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Keyboard controller• As its name indicates; it controls keyboard• Controls the transfer of data from the keyboard to the PC• The keyboard controller on the motherboard interacts with a controller located

inside the keyboard over a serial link.• When the keyboard controller on motherboard receives data from keyboard

• Checks for data parity• Translates the code• Places data in output buffer• Notifies processor for further processing

• It was common in older systems• Newer systems includes keyboard controller in super I/O chips

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Super I/O controller• Includes many controller functions that were previously performed by many

separate chips.• Combining these controllers

• Minimize space required for controllers in motherboard• Minimize the cost

• Major functions of super I/O controller are• Controlling data transfer functions of Serial ports• Driving Parallel ports• Support for floppy drive• Hard disk controllers circuits• Keyboard controller circuits

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Other chips• One of the fundamental design facts is that CPU work much faster than any other

device.• Forced designers to implement buffers that acts as interface between CPU and

slower devices to match speed.• Individual chips has been developed for this purpose:• DMA controller

• Allows devices to interact with RAM without involving CPU.

• CRT controller• Facilitates the display of PC

• Bus controller chip • This chip controls the flow of data on the motherboard’s buses

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Other chips• Clock generator

• Controls the timing of CPU operations

• UART (universal asynchronous receiver transmitter) • This chip is used to send and receive synchronous serial data

• Math coprocessor interface• Controls the flow of data between processor and math coprocessor

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The Buses• The busses are the nerve system of system board.• The busses are the PC's expressways. They are "wires" on the circuit board,

which transmit data between different components. • The bus architecture of the PC is made up of the wires, connectors, and devices

that move data and instructions around the PC.• Connects the controllers on the motherboard, the CPU, memory , I/O ports, and

expansion slots.• Buses are divided into two types

• System bus• I/O bus

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System bus• System bus

• Connects the CPU with RAM and maybe L2-cache• Designed to match a specific type of CPU• Processor technology determines dimensioning of the system bus• also called the local bus• Its speed and width depends on the type CPU installed on the system board.

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I/O buses• I/O busses

• Connect all I/O devices with the CPU and RAM.• I/O devices are those, which can receive or send data (disk drives, monitor, keyboard, etc. )

• A bridge connects the I/O busses with the system bus and to RAM.• The I/O busses differ from the system bus in speed

• Different I/O buses has been developed through the years• ISA

• Older low speed bus• PCI

• Newer high speed bus• PCI Express

• The most modern bus• USB

• Newer low speed bus

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Physical characteristics of Buses• The I/O buses consists of tracks on printed circuit boards, these tracks are

• Data tracks : moving one bit a time• Address tracks : identify address of data to be sent• Other tracks for : clock ticks, voltage, verification signals

• When data is sent on buses, the receiver of data is identified bus address• Each device has an address number• Address tracks contains these number that identify the receiver device

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ISA buses (Industry Standard Architecture)• Since about 1984, standard bus for PC I/O functions has been named ISA• Still used in all PC's to maintain backwards compatibility• ISA is 16 bit wide and runs at a maximum of 8 MHz. However, it requires 2-3

clock ticks to move 16 bits of data.• It only had 16 data channels

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PCI (Peripheral Component Interconnect)• PCI is 32 bit wide and has 33MHz clock speed• Has a buffer that CPU sends data to it and lowers CPU waiting time• PCI adapters can also transmit data to the buffer, regardless of whether the CPU

is free to process them.• Capable of transferring 132MB data per second

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Plug and Play (PnP) • The Plug and Play standard is part of the PCI specification• It means that all PCI adapter cards are self-configuring• developed by Microsoft and Intel• The idea was to provide a system where one can simply install an adapter and it

will work.• The adapter has to be able to inform the I/O bus which I/O addresses and IRQ’s it

can operate with.

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PCI EXPRESS• Successor to PCI• Developed in 2004

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References• “PC hardware a beginner’s guide” by Ron gilster• “PC architecture by Michael Karbo” 2005• “Illustrated guide to PC hardware” by Michael karbo 1998