Intel 80386 manual bit Architecture, High-performance Implementation

CHAPTER 1 HIGHLIGHTS

The 80386 is a high performance 32-bit micropro- cessor designed to drive the most advanced computer-based applications of today and tomor- row. CAE( CAD workstations, high resolution graphics, publishing, and office and factory automation are representative of today's appli- cations that are well-served by the 80386. Tomor- row's applications may be more constrained by the imagination of system designers than by the power and versatility of the 80386.

The 80386 offers the system designer many new and powerful capabilities, including unprece- dented performance of3 to 4 million instructions per second, a complete 32-bit architecture, a 4- gigabyte (232 bytes) physical address space, and on-chip support for paged virtual memory. While embodying the latest in microprocessor technology, the 80386 retains object code com- patibility with the wealth of software written for its predecessors, the 8086 and 80286. Of special interest is the 80386's virtual machine capability, which enables the 80386 to switch between programs running under different operating systems, such as Unix* and MS-DOS*. This facility enables OEMs to incorporate standard 16-bit application software directly into new 32-bit designs.

Combining the power and performance of a superminicomputer with the low cost and design versatility of a microprocessor, the 80386 can open new markets to microprocessor-based sys- tems. Applications that have not been feasible with slower microprocessors or cost-effective with superminicomputers are now practical with the 80386. Emerging applications such as machine vision, speech recognition, advanced robots, and expert systems, which have been largely experi- mental, can now be brought to market.

To effectively tackle the application challenges of tomorrow requires more than 32-bit registers, instructions, and buses. These fundamental facili- ties are only the starting point for the 80386. The

following sections summarize the 80386's 32-bit architecture along with its more innovative features:

oHigh-performance Implementation o Virtual Memory Support

e Configurable Protection

o Extended Debugging Support o Object Code Compatibility

1.132-bit Architecture

The 80386's 32-bit architecture provides the programming resources required to directly sup- port "large" applications-those characterized by large integers, large data structures, large programs (or large numbers of programs), and so on. The 80386's physical address space is 232 bytes, or 4 gigabytes; its logical address space is 246 bytes, or 64 terabytes. The 80386's eight 32-bit general registers can be used interchangeably both as instruction operands and addressing mode variables. Data types include 8-, 16-, and 32-bit integers and ordinals, packed and unpacked decimals, pointers, and strings of bits, bytes, words and doublewords. The 80386 has a com- plete set of instructions for manipulating these types, as well as for controlling execution. The 80386 addressing modes support efficient access to the elements of the standard data structures: arrays, records, arrays of records, and records containing arrays.

1.2High-performance Implementation

A 32-bit architecture does not guarantee high performance. To deliver the potential of the architecture requires leading-edge semiconductor technology, careful partitioning of functions, and attention to off-chip operations, particularly the interaction of processor and memory. Incor-

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