Types Of Local Buses

Types Of Local BusesVESA Bus PCI BusPCI ExpressAGPVESA Local BusThe first local bus was called as the VESA local bus(also called as VL-Bus or VLB).

The VESA(Video Electronics Standards Association) was introduced in 1992 by VESA committee , a non-profit organization originally founded by the NEC to develop video display and bus standards.

The VL-bus is a 32 bit bus . It is a direct extension of the 486 processor/ memory bus.

It can move data 32 bit at a time , enabling data to full 32 bit data width of the 486 chip.

Purpose of VESA BusThe main purpose of VESA bus is to increase the speed than ISA an EISA Bus standards.VESA bus is mainly designed the to support the high speed video controller. It also support the disk and network controller

Features of VESA busThe 32-bit VESA bus has 112 pins. 32 address and data lines It supports both 32 bit data transferIt has Maximum throughput 128MBps to 132 MBpsClock speed limit of 25-40MHzIt has strong based on Intel 80486 processorIt supports burst mode DMA transferIt has direct access to system memory at the speed of processor

4It can directly communicate to the motherboard component bypassing BIOSIt support the bus masteringIt is designed for use with single processor systemIt is backward compatible with ISA/EISA

VL BUS

Type- A With bufferingType-2Without BufferingDrawback of VESA BusIt has speed limitation.It does not support plug-and-playIt has timing problems, when multiple cards are usedIt can lead to loss of data integrity, if VL-bus is not implemented correctlyIt does not support multiprocessingIt does not support expansion to 64-bit Pentium systemPCI Local BusPCI (Peripheral component Interconnect) bus was introduced by Intel corporation in 1993.It is fast , cheap , flexible and high performance expansion bus architecture as compared to the earlier VL-bus and ISA.The PCI is a recent high bandwidth, processor independent bus.This bus is support various high speed device.PCI bus is designed to be easily interfaced with different microprocessor families , main memory, and a very wide range of I/O devices.PCI bus 32-bit 64-bitFeatures of 32-bit PCI busThe PCI bus is 32-bit has 124 pinClk speed limit is 33 MHz

Features of 64-bit PCI bus

Clk speed limit has 66MHzIt has 188 pins

Common features It is support full bus masteringPipeline Peer-to- peer card communicationMultiprocessing Play-n-plugBurst mode DMA transfers(both read and write)It is used to transfer data from peripherals such as disk controllers, video cards, modems, sound cards, network card, graphic cards and extra ports or USB.

It is independent platformSupport multiuser systemIt allow Direct data transfer among peripheral bypassing processorLow power consumptionSupport 3 or 4 cards on a system Coexist with ISA/EISA/MCAIt provides parity checking on address, data and command .

PCI Local busBridge/ memory controllerDRAMaudioMotion videoprocessorcacheLANSCSIExternal bus interfaceBase I/O functionsgraphicsISA/EISA MictrochannelPCI Express busPCI Express(peripheral component interconnect express) (PCIe or PCI-E)is high speed serial connection bus standard development by Intel corporation in 2004.It replace the PCI and PCI-X expansion buses It is fast, cheap and compatible or handling more bandwidth and high performance expansion bus architecture as compared to the earlier PCI and PCI-XThe PCI Express bus comes in several version (x1, x2, x4, x8, x12, x16and x32) which provide throughput of b/w 250MBps and 8gbps.,

Purpose of PCI Express BusImproved handshaking Better error detection mechanism Time dependent(real time) data transfersFeatures of PCI ExpressIt has 8-bit per laneIt is based in high speed serial communicationIt has maximum throughput of 250-Mbps to 8GBpsThe PCIe 1.0 version has Clk speed limit 2.5 GHz , PCIe 2.0 has 5GHz and PCIe 3.0 has 8GHZ .It has dedicated lane(connection) controlled by switch. Each PCI Express device doesnt have share bandwidthIt has software compatible but not compatible to hardware with PCI it is support full bus mastering, concurrency , plug-n-play and multiprocessing.The PCI Express x1 connector has 36 pin , x4 has 64 pins , x8 has 98 pins and x16 has 164pins It is able to combine multiple connection to form a single link it offers better graphics or network connection It is widely used in notebook ,desktop or serverIt support the up-plugging and down-plugging

AGP BUSAGP (Accelerated Graphics port) is interfaced standard developed by Intel corporation in 1997 .It is actually an expansion slots , specially designed for graphics cards The increasing demand of 3D-computing results in development of AGP slots Intel introduced AGP into chipset for its Pentium processor . It provides faster and dedicated interface between graphic card and processor

AGP versions VersionOperating modes Clock speed Number of bits Maximum throughputvoltageAGP 1.01x and 2x 66MHz 32 bit533 MBps3.3 vAGP 2.0 1x ,2x and 4x66 MHz32 bit1066 MBps1.5 vAGP 3.01x,2x,4x and 8x66 MHz32 bit2133 MBps1.5 vFeatures of AGP bus 32- bit busClk speed limit 66MHzIt has throughput of 366 MBps to 2.1GBpsIt has 132 pins It is specially designed for graphics card32 address lines 32 data lines It offers high speed data transfer to and from RAM

It support pipelining It support only ne graphics card on a system It provide better bandwidth within video systemIt support automatic system configuration to simplify installation It coexists with ISA/EISA/MCA/PCIIt has demultiplexing of address and data bus which improves bus efficiency