What is a coprocessor? A coprocessor is a specialized microprocessor with a limited, domain-focused instruction set optimized to perform arithmetic or numeric operations at very high speed alongside the main CPU.

Introduction / Context:
Coprocessors augment a general-purpose CPU by accelerating specific classes of operations. Classic examples include floating-point units (FPUs) like the Intel 8087, graphics processors (GPUs), and digital signal processors (DSPs) used as auxiliaries. They offload computationally intensive tasks, increasing system throughput and freeing the CPU for control logic and general tasks.

Given Data / Assumptions:

• A coprocessor focuses on a subset of operations (e.g., floating point, vector math, signal processing).
• Instruction set is specialized/limited relative to a full CPU.
• Works in tandem with the main processor via instruction prefixes, command queues, or shared memory/microcode interfaces.

Concept / Approach:
Specialization enables tailored hardware pipelines, wider datapaths, and optimized execution units for a particular numeric domain. This yields higher performance and efficiency than implementing the same operations solely in a general-purpose scalar pipeline. The main CPU orchestrates tasks and delegates heavy computation to the coprocessor when appropriate.

Step-by-Step Solution:

Verification / Alternative check:
Benchmarks show dramatic speedups for floating-point and vector workloads when using FPUs/SIMD versus software emulation on integer-only cores, validating the definition and purpose of a coprocessor.

Why Other Options Are Wrong:

• Incorrect: Denies the widely accepted definition.
• “Only a DMA controller” or “cache controller” describe other subsystems, not coprocessors.
• “Replaces the CPU entirely” is incorrect; a coprocessor complements, not replaces, the CPU.

Common Pitfalls:
Assuming coprocessors are limited to legacy FPUs; overlooking modern forms like GPUs and AI accelerators; confusing bus-mastering peripherals (e.g., DMA) with instruction-executing coprocessors.

Final Answer:
Correct