Serial vs. parallel — key wiring advantage What is the primary advantage of serial data transmission compared with parallel transmission for interconnections between digital systems?

Introduction / Context:
As data rates increased and links grew longer, serial interconnects (e.g., USB, PCIe, SATA, Ethernet) displaced wide parallel cables in many applications. This question emphasizes the wiring economy of serial links.

Given Data / Assumptions:

• Comparison at system or inter-board level, not inside a short PCB bus.
• Modern differential serial signaling (twisted pair) is assumed.
• Clock recovery or embedded clock is available for serial.

Concept / Approach:

Serial links reduce conductor count drastically because data travels one bit at a time over a differential pair (or even a single wire in some protocols). With proper encoding and equalization, serial channels can run at very high bit rates over relatively long distances with fewer wires and smaller connectors.

Step-by-Step Solution:

Verification / Alternative check:

Compare a classic 25-pin parallel cable to a two-pair Ethernet cable; or PCI (parallel) to PCIe (serial lanes). The reduction in pins and improved signal integrity are compelling reasons for serial adoption.

Why Other Options Are Wrong:

• It is slower: modern serial links are extremely fast; “slower” is not inherent.
• More people use it: not a technical reason.
• It is faster: sometimes true vs. a given parallel link, but the defining advantage is wiring simplicity.
• No clock reference: serial links use embedded clocks or explicit references.

Common Pitfalls:

• Assuming serial is always faster; bandwidth depends on protocol and encoding.
• Ignoring latency; some serial protocols add link-layer overhead.

Final Answer:

Only one pair of wires is required.