page_title: Peripheral Component Interconnect
section_title: History
hierarchical_section_title: Peripheral Component Interconnect / History
caption_attribution_description: English: Adaptec AHA-2940AU Ultra SCSI host adapter. It is equipped with an 50 pin connector for internal drives as well as a HPDB50 port for external devices.
context_page_description: Peripheral Component Interconnect is a local computer bus for attaching hardware devices in a computer and is part of the PCI Local Bus standard. The PCI bus supports the functions found on a processor bus but in a standardized format that is independent of any particular processor's native bus. Devices connected to the PCI bus appear to a bus master to be connected directly to its own bus and are assigned addresses in the processor's address space. It is a parallel bus, synchronous to a single bus clock.
  Attached devices can take either the form of an integrated circuit fitted onto the motherboard itself or an expansion card that fits into a slot. The PCI Local Bus was first implemented in IBM PC compatibles, where it displaced the combination of several slow Industry Standard Architecture slots and one fast VESA Local Bus slot as the bus configuration. It has subsequently been adopted for other computer types. Typical PCI cards used in PCs include: network cards, sound cards, modems, extra ports such as USB or serial, TV tuner cards and disk controllers. PCI video cards replaced ISA and VESA cards until growing bandwidth requirements outgrew the capabilities of PCI.
context_section_description: Work on PCI began at Intel's Architecture Development Lab (IAL) c. 1990. A team of primarily IAL engineers defined the architecture and developed a proof of concept chipset and platform (Saturn) partnering with teams in the company's desktop PC systems and core logic product organizations.
  PCI was immediately put to use in servers, replacing MCA and EISA as the server expansion bus of choice. In mainstream PCs, PCI was slower to replace VESA Local Bus (VLB), and did not gain significant market penetration until late 1994 in second-generation Pentium PCs. By 1996, VLB was all but extinct, and manufacturers had adopted PCI even for 486 computers. EISA continued to be used alongside PCI through 2000. Apple Computer adopted PCI for professional Power Macintosh computers (replacing NuBus) in mid-1995, and the consumer Performa product line (replacing LC PDS) in mid-1996.
  The 64-bit version of plain PCI remained rare in practice though, although it was used for example by all (post-iMac) G3 and G4 Power Macintosh computers.
  Later revisions of PCI added new features and performance improvements, including a 66 MHz 3.3 V standard and 133 MHz PCI-X, and the adaptation of PCI signaling to other form factors. Both PCI-X 1.0b and PCI-X 2.0 are backward compatible with some PCI standards. These revisions were used on server hardware but consumer PC hardware remained nearly all 32 bit, 33 MHz and 5 volt.
  The PCI-SIG introduced the serial PCI Express in c. 2004. Since then, motherboard manufacturers have included progressively fewer PCI slots in favor of the new standard. Many new motherboards do not provide PCI slots at all, as of late 2013.
caption: A typical 32-bit, 5 V-only PCI card, in this case, a SCSI adapter from Adaptec
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