Types of System Buses - Quick Reference


Industry Standard Architecture (ISA)

  • Introduced in 1984 with the IBM PC AT
  • 8- or 16-bit bus
  • 98-pin connector
  • 8 MB/sec bandwidth

Industry Standard Architecture (ISA) Slot

Extended Industry Standard Architecture (EISA)

  • Introducted in 1987 to compete against MCA bus
  • 32-bit bus
  • Dual purpose bus
  • Replace by better performing PCI bus

Micro Channel Architecture (MCA)

  • Developed by IBM in 1987
  • Not widely adopted by vendors as IBM charged royalties for the rights to use it
  • 116-pin connector
  • Made extinct by the license-free EISA bus and later by the PCI bus

VESA Local Bus (VESA)

  • Developed in 1992 as an extension of video memory
  • 116-pin connector
  • Replaced by better performing AGP bus

Peripheral Component Interconnect (PCI)

  • Standard bus on almost all computers of the era
  • Developed with open standards (no licensing fee to use)
  • Hot-swappable
  • Plug-and-play compatible
  • 32-bit bus
  • Can support 5 devices at a time

Peripheral Component Interconnect (PCI) Slot


  • 64-bit wide bus

Accelerated Graphics Port (AGP)

  • Introduced by Intel in 1997
  • Used mostly with AGP-compatible video cards
  • Original AGP standard (AGP 1x) offered data transfer rate of 264MB/sec
  • 32-bit wide bus
  • 132-pin connector
  • AGP 2x, 4x, and 8x offered data transfer rate of 528MB/sec, 1GB/sec,and 2GB/sec respectively
  • Replaced by PCI Express in late 2000s

PCI Express (PCI-E, PCIe)

  • Developed by Intel in 2004
  • Formerly known as 3GIO
  • 1-bit wide bus (serial communication)
  • Bandwidths:
    • PCI-E 1x: 250 MB/sec
    • PCI-E 2x: 500 MB/sec
    • PCI-E 4x: 1000 MB/sec
    • PCI-E 8x: 2000 MB/sec
    • PCI-E 16x: 4000 MB/sec
    • PCI-E 32x: 8000 MB/sec

Intelligent Input/Output (I2O)

  • Designed in 1996 by Intel and I20
  • Works along with a PCI bus
  • Uses special input and output drivers to "think for itself" thus freeing up computer resources
  • End of life in October 2000

InfiniBand Architecture (IBA)

  • Conceived in 1999
  • High-speed / high-output bus to replace PCI
  • Low latency
Recommended Reading

"Very comprehensive easy format to follow."

Amazon Reviewer

(Amazon Affiliate Link)