Computer Architecture — First Intel Processor with a 32-bit External Bus Which Intel x86 processor was the first to feature a true 32-bit external data bus architecture?

Introduction / Context:
Transitioning from 16-bit to 32-bit architectures marked a major leap in personal computing. Beyond internal registers, the width of the external data bus determines how much data can be moved per memory transaction, influencing overall bandwidth and performance.

Given Data / Assumptions:

• We are focusing on the first Intel x86 chip with a 32-bit external data bus.
• 'External bus' refers to the CPU's data path to memory and chipset, not just internal registers.
• Model naming variations (e.g., 486SX vs 486DX) can confuse capabilities.

Concept / Approach:

The Intel 80386DX introduced a 32-bit architecture with a 32-bit external data bus and a 32-bit address bus, enabling full 32-bit computing in PCs. Earlier 80286 parts were 16-bit externally. Later processors such as the 80486 and Pentium also had 32-bit buses, but the 386DX was the first.

Step-by-Step Solution:

Check 80286: 16-bit external bus → not first.Check 80386DX: 32-bit external data bus → first to provide it.Check 80486SX/DX and Pentium: later generations → not first.Choose 386DX.

Verification / Alternative check:

Technical references list 80386DX with a 32-bit data bus; 80386SX used a 16-bit external bus for lower-cost systems, confirming DX as the milestone part.

Why Other Options Are Wrong:

286: 16-bit external bus.486SX/Pentium: Feature 32-bit buses but were released after the 386DX.

Common Pitfalls:

Confusing internal register width with external bus width; they are related but not identical across some models (e.g., 386SX).

Final Answer:

386DX