PCI

/ˌpiː-siː-ˈaɪ/

n. “The standard expansion bus that connected peripherals before PCIe.”

PCI, short for Peripheral Component Interconnect, is a local computer bus standard introduced in the early 1990s that allowed expansion cards, such as network adapters, sound cards, and graphics cards, to connect directly to a computer’s motherboard. It provided a shared parallel interface for data transfer between the CPU and peripheral devices.

Key characteristics of PCI include:

• Parallel Bus: Uses multiple data lines to transmit several bits simultaneously.
• Bus Mastering: Devices could take control of the bus to transfer data independently of the CPU.
• Shared Bandwidth: All devices on the same PCI bus share total bus bandwidth, potentially limiting speed as more devices are added.
• Plug and Play: Supported automatic device configuration, reducing manual setup.
• Legacy Standard: Mostly replaced by PCIe for higher-speed, point-to-point connections.

Conceptual example of PCI usage:

# Installing a PCI network card in a 1998 desktop
Motherboard has multiple PCI slots
Card communicates with CPU via shared PCI bus
Bandwidth shared with any other PCI devices installed

Conceptually, PCI is like a shared roadway: multiple cars (devices) travel together on the same lanes, which works well for moderate traffic but can become congested with more cars.

In essence, PCI was a foundational standard for connecting peripheral devices to PCs, enabling expansion and modularity before the era of high-speed, dedicated links like PCIe.