In PC hardware, which motherboard form factor introduced the single 20-pin main power connector standard on the board?

Introduction / Context:
Motherboard form factors define physical dimensions, mounting holes, I/O placement, and power connector standards. Recognizing which form factor standardized the single 20-pin main power connector helps in correct PSU selection and system compatibility.

Given Data / Assumptions:

• We compare ATX with earlier AT and Baby AT form factors.
• Focus is on the main motherboard power connector standard.
• Historical mainstream desktop platforms are implied.

Concept / Approach:
AT and Baby AT used dual 6-pin connectors (often labeled P8 and P9) that had to be oriented correctly. ATX replaced this with a unified 20-pin connector, simplifying installation and improving power delivery and safety. Later ATX revisions expanded to 24 pins, but the question targets the original 20-pin standard.

Step-by-Step Solution:

Verification / Alternative check:
Technical references and PSU labeling (ATX P1 20-pin) confirm the ATX origin of the 20-pin standard before the move to 24 pins.

Why Other Options Are Wrong:

• AT: Used P8/P9 dual connectors, not one 20-pin.
• Baby AT: Same power scheme as AT.
• All of the above: False because only ATX matches the 20-pin criterion.
• None of the above: False because ATX is correct.

Common Pitfalls:
Confusing modern 24-pin ATX with the original 20-pin, and assuming AT boards ever used a single multi-pin connector (they did not).

Final Answer:
ATX