PCI(Peripheral Component Interconnect)

PCI(피씨-아이]는 고속운영을 위해 마이크로프로세서와 가깝게 위치해 있는 확장 슬롯들에 부착된 장치들 간의 상호접속 시스템이다. PCI를 사용하면 컴퓨터는 새로운 PCI 카드들과, 현재 가장 일반적인 확장카드의 종류인 ISA 확장카드를 함께 지원할 수 있다. 인텔에 의해 설계된 초기의 PCI는 VESA 로컬버스와 비슷했지만, PCI 2.0부터는 더 이상 로컬버스가 아니며, 마이크로프로세서 디자인과는 독립적으로 설계되었다. PCI는 20~33 MHz 범위의 마이크로프로세서 클록 속도에 동기화 되도록 설계되었다.
PCI는 이제 인텔 펜티엄 프로세서 기반의 시스템은 물론, PowerPC 기반의 시스템을 비롯한 대부분의 새로운 데스크탑 컴퓨터에 설치되었다. PCI는 124 핀의 접속으로 한번에 32 비트를 전송하며, 확장된 제품인 188 핀 접속에서는 64 비트를 전송한다. PCI는 주소와 데이터 신호를 전송하기 위해 모든 동적 경로들을 사용하며, 첫 번째 클록 사이클에 주소를 보내고 그 다음에 데이터를 보낸다. 많은 량의 데이터를 보낼 때에는 첫 번째 사이클에 시작 주소를 보낸 다음, 이어지는 일정횟수의 사이클 동안 계속해서 데이터 전송을 하는 것도 가능하다.
<출처 : 김동근의 텀즈 * 컴퓨터 용어사전 http://www.terms.co.kr/>

The Peripheral Component Interconnect, or PCI Standard (in practice almost always shortened to PCI) specifies a computer bus for attaching peripheral devices to a computer motherboard. These devices can take any one of the following forms:

 

   * An integrated circuit fitted onto the motherboard itself, called a planar device in the PCI specification.
   * An expansion card that fits into a socket.
The PCI bus is common in modern PCs, where it has displaced ISA and VESA Local Bus as the standard expansion bus, but it also appears in many other computer types. The bus will eventually be succeeded by PCI Express, which is standard in most new computers, and other technologies.

 

The PCI specification covers the physical size of the bus (including wire spacing), electrical characteristics, bus timing, and protocols. The specification can be purchased from the PCI Special Interest Group (PCISIG).

 

Conventional hardware specifications

These specifications represent the most common version of PCI used in normal PCs.

   * 33.33 MHz clock with synchronous transfers
   * peak transfer rate of 133 MB per second for 32-bit bus width

      (33.33 MHz × 32 bits ÷ 8 bits/byte = 133 MB/s)
   * peak transfer rate of 266 MB/s for 64-bit bus width
   * 32-bit or 64-bit bus width
   * 32-bit address space (4 gigabytes)
   * 32-bit I/O port space (now deprecated)
   * 256-byte configuration space
   * 5-volt signaling
   * reflected-wave switching

 

Variants

 – Conventional

   * Later versions of PCI allow (and in the latest versions require) 3.3V slots (keyed differently) on motherboards and allow
     for cards that are either double keyed for both voltages or even 3.3V only.
   * PCI 2.2 allows for 66 MHz signalling (requires 3.3 volt signalling) (peak transfer rate of 533 MB/s)
   * PCI 2.3 permits use of 3.3 volt and universal keying, but does not allow 5 volt keyed add in cards.
   * PCI 3.0 is the final official standard of the bus, completely removing 5-volt capability.
   * PCI-X doubles the width to 64-bit, revises the protocol, and increases the maximum signaling frequency to 133 MHz
     (peak transfer rate of 1014 MB/s)
   * PCI-X 2.0 permits a 266 MHz rate (peak transfer rate of 2035 MB/s) and also 533 MHz rate, expands the configuration
      space to 4096 bytes, adds a 16-bit bus variant and allows for 1.5 volt signaling
   * Mini PCI is a new form factor of PCI 2.2 for use mainly inside laptops
   * CardBus is a PC card form factor for 32-bit, 33 MHz PCI
   * CompactPCI, uses Eurocard-sized modules plugged into a PCI backplane.
   * PC/104-Plus is an industrial bus that uses the PCI signal lines with different connectors.


Physical card dimensions

 – Full-size card
The original “full-size” PCI card is specified as a height of 107 mm (4.2 inches) and a depth of 312 mm (12.283 inches). The height includes the edge card connector. However, most modern PCI cards are half-length or smaller (see below) and many PCs cannot fit a full size card.


 – Backplate
In addition to these dimensions the physical size and location of a card’s backplate are also standardized. The backplate is the part that fastens to the card cage to stabilize the card and also contains external connectors,so it usually attaches in a window so it is accessible from outside the computer case.

The card itself can be a smaller size, but the backplate must still be full-size and properly located so that the card fits in any standard PCI slot.


 – Half-length extension card (de-facto standard)
This is in fact the practical standard now – the majority of modern PCI cards fit inside this length.

   * Width: 0.6 inches (15.24 mm)
   * Depth: 6.9 inches (175.26 mm)
   * Height: 4.2 inches (106.68 mm)

 

 – Low profile (half height) card
The PCI organisation has a defined a standard for “low profile” cards, which basically fit in the following ranges:

   * Height: 1.42 inches (36.07 mm) to 2.536 inches (64.41 mm)
   * Depth: 4.721 inches (119.91 mm) to 6.6 inches (167.64 mm)
The bracket is also reduced in height, to a standard 3.118 inches (79.2 mm).

These cards may be known by other names such as “slim”.



 – Mini PCI
This is a specialist version of PCI slot intended for laptops and the like, and is not usually used by consumers.


 – Other physical variations
Typically consumers systems specify “N x PCI slots” without specifying actual dimensions of the space available. In some small form-factor systems, this may not be sufficient to allow even “half-length” PCI cards to fit. Despite this limitation, these systems are still useful because many modern PCI cards are considerably smaller than half-length.


 – Card keying
Typical PCI cards present either one or two key notches, depending on their signaling voltage. Cards requiring 3.3 volt have a notch near the front of the card (where the external connectors are) while those requiring 5 volt have a notch near on the other side. So called “Universal cards” have both key notches and can accept both types of signal.

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