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Conventional PCI, often shortened to PCI, is a local computer bus for attaching hardware devices in a computer. PCI is the initialism for Peripheral Component Interconnect〔.〕 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.〔Hamacher et al (2002), ''Computer Organization'', 5th ed., McGraw-Hill.〕 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 (called a ''planar device'' in the PCI specification) 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 ISA 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. The preferred interface for video cards then became AGP, itself a superset of conventional PCI, before giving way to PCI Express. The first version of conventional PCI found in consumer desktop computers was a 32-bit bus using a 33 MHz bus clock and 5 V signalling, although the PCI 1.0 standard provided for a 64-bit variant as well. These have one locating notch in the card. Version 2.0 of the PCI standard introduced 3.3 V slots, physically distinguished by a flipped physical connector to preventing accidental insertion of 5 V cards. Universal cards, which can operate on either voltage, have two notches. Version 2.1 of the PCI standard introduced optional 66 MHz operation. A server-oriented variant of conventional PCI, called PCI-X (PCI Extended) operated at frequencies up to 133 MHz for PCI-X 1.0 and up to 533 MHz for PCI-X 2.0. An internal connector for laptop cards, called Mini PCI, was introduced in version 2.2 of the PCI specification. The PCI bus was also adopted for an external laptop connector standard—the CardBus. The first PCI specification was developed by Intel, but subsequent development of the standard became the responsibility of the PCI Special Interest Group (PCI-SIG). Conventional PCI and PCI-X are sometimes called Parallel PCI in order to distinguish them technologically from their more recent successor PCI Express, which adopted a serial, lane-based architecture.〔 Conventional PCI's heyday in the desktop computer market was approximately the decade 1995-2005. PCI and PCI-X have become obsolete for most purposes; however, they are still common on modern desktops for the purposes of backwards compatibility and the low relative cost to produce. Many kinds of devices previously available on PCI expansion cards are now commonly integrated onto motherboards or available in universal serial bus and PCI Express versions. ==History== Work on PCI began at Intel's Architecture Development Lab circa 1990. A team of Intel engineers (composed primarily of ADL 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. The original PCI architecture team included, among others, Dave Carson, Norm Rasmussen, Brad Hosler, Ed Solari, Bruce Young, Gary Solomon, Ali Oztaskin, Tom Sakoda, Rich Haslam, Jeff Rabe, and Steve Fischer. 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.〔VLB was designed for 486-based systems, yet even the more generic PCI was to gain prominence on that platform.〕 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.〔(Identify a variety of PCI slots ), LaCie〕 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. The PCI-SIG introduced the serial PCI Express in circa 2004. At the same time, they renamed ''PCI'' as ''Conventional PCI''. Since then, motherboard manufacturers have included progressively fewer Conventional PCI slots in favor of the new standard. Many new motherboards do not provide conventional PCI slots at all, as of late 2013. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Conventional PCI」の詳細全文を読む スポンサード リンク
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