First Intel microprocessor with on-chip cache Identify the first Intel x86 microprocessor that integrated cache memory directly on the CPU die.

Introduction / Context:
On-chip cache dramatically reduced average memory access latency and enabled higher instruction throughput. Knowing when cache first appeared on x86 clarifies the performance leaps in successive generations.

Given Data / Assumptions:

• 80386 introduced 32-bit architecture but did not integrate an on-die cache.
• 80486 integrated an on-chip unified cache and an on-chip FPU (in 486DX).
• Pentium and later generations expanded cache sizes and levels.

Concept / Approach:
Chronologically, the 80486 was the first x86 to include an on-chip cache (commonly 8 KB unified). This significantly improved performance even at similar clock speeds compared to the 80386.

Step-by-Step Solution:
Evaluate timeline → 80386 (no on-die cache).Next generation → 80486 (adds on-chip cache, pipe improvements).Therefore → 80486 is the correct answer.

Verification / Alternative check:
Historical processor datasheets and architecture summaries consistently attribute on-chip cache introduction to the 80486 family.

Why Other Options Are Wrong:

• 80386: cacheless on die.
• Pentium/Pentium Pro: later families with larger, more complex cache hierarchies, but not the first.

Common Pitfalls:
Assuming Pentium first introduced all modern features; many started with 80486.

Final Answer:
80486