Bus Speeds: ISA vs PCI vs USB vs IDE vs SCSI vs Firewire

Mostly copied from http://www.moreprocess.com /devices/types-of-bus-isa-pci-ide-usb-scsi-ieee-1394


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. The ISA bus can transfer 8 or 16 bits at one time. ISA's 8 bit bus can run at 4.77 MHz the clock speed of the IBM PC and IBM XT's 8088 CPU and a data transfer of just over 2 MBytes/s. The 16 bit (2 byte) IBM AT's 80286 CPU ran originally at 8 MHz and about 8 MBytes/s. The ISA is still in use with parallel printers.

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 ran originally at 33 Mhz, with a data transfer of 250 Mbytes/s. PCI Express is used with modern graphics cards at 1 gbyte/s (or more), also network cards.

3) IDE (Integrated Drive Electronics) bus: IDE bus is used for connecting disks and CDROMs to the computer. Retroactively termed Parallel ATA (AT attachment) with the first such 16-bit drives appearing in Compaq PCs in 1986. A short-lived, 8-bit implementation of ATA was created for the IBM XT and similar machines. The latest versions of Parallel ATA support up to 133 MByte/s.

4) SCSI (Small Computer System Interface) bus: It is a high performance 16-bit bus which is used for fast disks, scanners, and for devices which require high bandwidth. It has a data rate of 640 MB/s.

5) USB (Universal Serial Bus), a single bit bus: It is used for connecting keyboard and mouse, and other USB devices such as wireless network adapters 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 60 MB/s. There is also a USB 3.0, that can travel at 640 MB/s, though interference issues have been reported with wireless devices.

6) IEEE 1394 or FireWire: IEEE 1394 is used for high speed data transfer. It was built by Apple, though Apple have moved away from it. It can transfer data at a rate of up to 400 MB/s. It is a single bit serial bus which is used for connecting cameras, and other multimedia devices.

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