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PERIPHERAL COMPONENT INTERCONNECT (PCI) BUS
What is a bus?
Communication pathway connecting two or more devices
Typical desktop PC has two main buses:
1)System bus or Local bus - connects CPU and memory
- fastest bus

2)PCI bus -connects hard-disks , sound cards
-slower bus
PCI BUS
Parallel bus
Developed by Intel in 1992
Interconnects chips,expansion boards and processor memory subsystems
5 volt, 33MHz, 32-bit bus with a basic data transfer rate of 133 Mb/s
Why PCI ?
The original PC bus developed by IBM in 1982 was 16 bits wide and operated at 4.77 MHz
This was known as ISA bus having datarate of 9Mbytes per sec!
Gradually peripherals such as video cards and hard- drives required a higher bandwidth
It detached the speed of the peripheral bus from that of the memory
Hence PCI devices can operate at their own independent speed
Dual Independent Bus (DIB)
Backside Bus
Frontside Bus
PCI
Direct access to system memory for connected devices
Uses a bridge to connect to the frontside bus and therefore to the CPU
Real Motherboard
PCI BUS Performance
What makes the PCI bus one of the fastest I/O bus used today?
Four features make this possible:
Burst Mode: allows multiple sets of data to be sent.
Full Bus Mastering: the ability of devices on the PCI bus to perform transfers directly.
High Bandwidth : allows for increased speed of the PCI
Plug and Play(PnP)
How a Device Works
Example: PCI-based sound card
The sound card will convert the analog signal to a digital signal.
The digital audio data carried across the PCI bus to the bus controller, which determines which device on the PCI device has the priority to send data to the central processing unit (CPU) and whether the data will go directly to the CPU or to the system memory.
If the sound card is in recording mode, the bus controller will assign a high priority to the data coming from the sound card. It will send the sound cards data over the bus bridge to the system bus.
The system bus will save the data in system memory. When the recording is complete, then it will be up to the user to save the data from the sound card on either the hard drive, or will remain in memory for additional processing.
Typical PCI Card
PCI Slots in Motherboard
How to Install
PCI Technology
Conventional PCI
PCI-X
PCI Express
Conventional PCI
Plug-and-Play Functionality
32 bit and operates at 33 MHz
PCI 2.1 supporting both 3.3V and 5V
PCI 2.3 supporting only 3.3V
PCI-X
Based on existing PCI architecture
64-Bit slots with support for 3.3V and Universal PCI
PCI-X 1.0 has two speed grades:66MHz and 133MHz
PCI-X 2.0 provides two additional speed grades : 266 MHz and 533 MHz
PCI-Express
PCI bus with highest performance
Serial connection
switch that controls several point-to-point connections
enable transfer rates of up to 2.5Gbits/second
Conclusion
Due to the need for growing data transfer rates among IO devices, the original PCI Architecture has become outdated
A new model of PCI, called PCI Express will replace the dated architecture giving it life for another decade
THANK YOU…
Bus Arbitration
Centralised
Single hardware device controlling bus access
Bus Controller
Arbiter
May be part of CPU or separate