computer science

Peripheral Component Interconnect

Peripheral Component Interconnect is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Peripheral Component Interconnect rather than just read about it. In short: Peripheral Component Interconnect (PCI) 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 given processor's native bus.

Key takeaways

Peripheral Component Interconnect belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Peripheral Component Interconnect to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Peripheral Component Interconnect from memory before moving on to harder problems.

Reference excerpt

Peripheral Component Interconnect (PCI) 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 given 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 (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 Industry Standard Architecture (ISA) slots and one fast VESA Local Bus (VLB) 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 Universal Serial Bus (USB) or serial, TV tuner cards and hard disk drive host adapters. PCI video cards replaced ISA and VLB cards until rising bandwidth needs outgrew the abilities of PCI. The preferred interface for video cards then became Accelerated Graphics Port (AGP), a superset of PCI, before giving way to PCI Express. 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). The first version of PCI found in retail desktop computers was a 32-bit bus using a 33 MHz bus clock and 5 V signaling, 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 prevent 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 PCI, PCI Extended (PCI-X) 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 as an external laptop connector standard – CardBus. PCI and PCI-X are sometimes referred to as either Parallel PCI or Conventional PCI to distinguish them technologically from their more recent successor PCI Express, which adopted a serial, lane-based architecture. PCI's heyday in the desktop computer market was approximately 1995 to 2005. PCI and PCI-X have become obsolete for most purposes and have largely disappeared from many other modern motherboards since 2013; however they are still common on some modern desktops as of 2020 for the purposes of backward compatibility and the relative low cost to produce. Another common modern application of parallel PCI is in industrial PCs, where many specialized expansion cards, used here, never transitioned to PCI Express, just as some ISA cards never transitioned to PCI. Many kinds of devices formerly available on PCI expansion cards are now commonly integrated onto motherboards or available in USB and PCI Express versions.

History

Work on PCI began at the Intel Architecture Labs (IAL, also Architecture Development Lab) 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 Micro Channel architecture (MCA) and Extended Industry Standard Architecture (EISA) as the server expansion bus of choice. In mainstream PCs, PCI was slower to replace 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 Intel 80486 (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 Processor Direct Slot (PDS)) in mid-1996. Outside the server market, 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 gradually included fewer or zero PCI slots in favor of the new standard. Bridge adapters allow the use of legacy PCI cards with PCI Express motherboards.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Peripheral Component Interconnect

Start with the simplest possible case. Write down what Peripheral Component Interconnect claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Peripheral Component Interconnect before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Peripheral Component Interconnect ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Peripheral Component Interconnect

In research: Peripheral Component Interconnect appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Peripheral Component Interconnect in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Peripheral Component Interconnect is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer-related introductions in 1993, IBM PC compatibles, Macintosh internals, so understanding it makes those chapters shorter.
In everyday life: Look for Peripheral Component Interconnect outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Peripheral Component Interconnect in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Peripheral Component Interconnect means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Peripheral Component Interconnect out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Peripheral Component Interconnect in simple terms?

Why does Peripheral Component Interconnect matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Peripheral Component Interconnect?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Peripheral Component Interconnect.