# Intel 80387

> floating-point unit for the Intel 80386 series of microprocessors

**Wikidata**: [Q2486154](https://www.wikidata.org/wiki/Q2486154)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Intel_80387)  
**Source**: https://4ort.xyz/entity/intel-80387

## Summary
The Intel 80387 is a floating-point unit (FPU) coprocessor designed to work with the Intel 80386 microprocessor. It was manufactured by Intel to provide hardware acceleration for floating-point arithmetic operations.

## Key Facts
- Instance of: floating-point unit
- Manufacturer: Intel
- Instruction set: x87
- Aliases: 387, i387, 387DX, i387DX, Microprocesador 80387, 80387
- Wikipedia title: Intel 80387
- Commons category: Intel 80387
- Available in Wikipedia languages: commons, de, en, es, fr, hu, it, ja, no, pt
- Google Knowledge Graph ID: /g/121v842h
- Sitelink count: 10

## FAQs
### Q: What is the Intel 80387?
A: The Intel 80387 is a floating-point unit coprocessor designed for the Intel 80386 series of microprocessors. It provides hardware acceleration for floating-point arithmetic operations.

### Q: Who manufactured the Intel 80387?
A: The Intel 80387 was manufactured by Intel, the American multinational technology company headquartered in Santa Clara, California.

### Q: What instruction set does the Intel 80387 use?
A: The Intel 80387 uses the x87 instruction set for floating-point operations.

## Why It Matters
The Intel 80387 represents a significant advancement in microprocessor technology by providing dedicated hardware for floating-point calculations. Before the 80387, floating-point operations were performed in software, which was much slower than hardware-based computation. By offloading these complex mathematical operations to a specialized coprocessor, the 80387 dramatically improved the performance of scientific, engineering, and graphics applications that rely heavily on floating-point arithmetic. This coprocessor enabled personal computers to handle more sophisticated computational tasks, making them viable tools for professional applications that previously required mainframe computers. The 80387's integration with the 80386 architecture helped establish Intel's dominance in the PC market and set the standard for future processor designs that would eventually integrate floating-point units directly onto the main processor die.

## Notable For
- First floating-point coprocessor designed specifically for the 80386 architecture
- Provided significant performance boost for floating-point intensive applications
- Used the x87 instruction set, which became a standard for x86 floating-point operations
- Featured 80-bit extended precision internal registers
- Enabled more sophisticated scientific and engineering applications on personal computers

## Body
### Technical Specifications
The Intel 80387 was designed as a companion chip to the Intel 80386 microprocessor, providing hardware floating-point capabilities that the 80386 lacked natively. The coprocessor operates at the same clock speed as the main processor and shares the same bus interface, allowing for seamless integration.

### Architecture
The 80387 features an internal architecture optimized for floating-point operations, including an 80-bit extended precision format for internal calculations. This provides greater accuracy than the standard 64-bit double precision format used in many applications. The coprocessor includes eight 80-bit floating-point registers that can be addressed as a stack, following the x87 architecture.

### Performance Impact
By handling floating-point operations in hardware, the 80387 could perform calculations several times faster than software emulation. This was particularly important for applications in scientific computing, computer-aided design, and computer graphics, where floating-point operations are frequent and performance-critical.

### Integration with 80386
The 80387 communicates with the 80386 through a dedicated interface, allowing the main processor to continue executing integer instructions while floating-point operations are being processed. This parallel processing capability improved overall system throughput for mixed workloads.

### Legacy
The x87 instruction set architecture introduced with the 80387 became the foundation for floating-point operations in x86 processors. While modern processors have integrated floating-point units directly onto the main processor die, the architectural concepts and instruction set developed for the 80387 continue to influence processor design today.