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SCSI is standard electronic interfaces that allow personal computers to communicate with peripheral hardware such as disk drives, tape drives etc.
Peripheral Component Interconnect (PCI), as its name implies is a standard that describes how to connect the peripheral components of a system together in a structured and controlled way.

Now my question is what makes them different,the way the data is transferd ? or the hardware ?

Thanks for your help .

Harish Basavaraju
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Quote from here:

For connecting different devices to a computer different buses are used. Each bus typically has a different data transfer speed.

1) ISA (Industry Standard Architecture) bus: ISA bus was created by IBM in 1981. ISA bus can transfer 8 or 16 bits at one time. ISA 8 bit bus can run at 4.77 MHz and 16 bit at 8.33 MHz.

2) PCI (Peripheral Component Interconnect) bus: PCI bus was created by Intel in 1993. PCI bus can transfer 32 or 64 bits at one time. PCI bus can run at 33 Mhz.

3) IDE (Integrated Drive Electronics) bus: IDE bus is used for connecting disks and CDROMs to the computer.

4) USB (Universal Serial Bus): It is used for connecting keyboard and mouse, and other USB devices to the computer. A USB bus has a connector with four wires. Two wires are used for supplying electrical power to the USB devices. USB 1.0 has a data rate of 1.5 MB/s and USB 2.0 which is a high speed one has a data rate of 35 MB/s.

5) SCSI (Small Computer System Interface) bus: It is a high performance bus which is used for fast disks, scanners, and for devices which require high bandwidth. It has a data rate of 160 MB/s.

6) IEEE 1394 or FireWire: IEEE 1394 is used for high speed data transfer. It can transfer data at a rate of up to 400 MB/s. It is a bit serial bus which is used for connection cameras, and other multimedia devices.

So basically, different buses are made for different devices/scenarios.

smwikipedia
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SCSI is only used for storage devices and must have an interface controller.

PCI can be used for a variety of peripherals. For example Graphics cards and NICs.

There are many similarities between the two as well. For example both uses the south bridge. Hope this helps you. :)

Marcel De Villiers
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  • Oh and both uses IRQ(interrupt requests) and DMA(dynamic memory access). Both are also parallel connectors, thus data transfer is the same. Also, although I am unsure, I vaguely remember something about SCSI being slower. – Marcel De Villiers Jun 27 '13 at 09:47
  • Is PCI restricted for devices other than sorage ?. – Harish Basavaraju Jun 27 '13 at 09:54
  • I don't think SCSI is restricted to storage devices from a theoretical point of view, but I have never heard of SCSI being used for anything other than storage devices. SCSI is rarely used in the industry today since a fast SCSI device have a max theoretical throughput of around 10Mb/s. SATA3 for example can reach a theoretical throuhgput of 600Mb/s – Marcel De Villiers Jun 28 '13 at 10:49