Intel 80286, 80287 manual AN Introduction to, Microsystem

PREFACE

AN INTRODUCTION TO THE 80286

This supplement describes the 80287 Numeric Processor Extension (NPX) for the 80286 microproces- sor. Below is a brief overview of 80286 concepts, along with some of the nomenclature used throughout this and other Intel publications.

The 80286 Microsystem

The 80286 is a new VLSI microprocessor system with exceptional capabilities for supporting large- system applications. Based on a new-generation CPU (the Intel 80286), this powerful microsystem is designed to support multiuser reprogrammable and real-time multitasking applications. Its dedicated system support circuits simplify system hardware; sophisticated hardware and software tools reduce both the time and the cost of product development.

The 80286 is a virtual-memory microprocessor with on-chip memory management and protection. The 80286 microsystem offers a total-solution approach, enabling you to develop high-speed, interactive, multiuser, multitasking-and multiprocessor-systems more rapidly and at higher performance than ever before.

•Reliability and system up-time are becoming increasingly important in all applications. Information must be protected from misuse or accidental loss. The 80286 includes a sophisticated and flexible four-level protection mechanism that isolates layers of operating system programs from application programs to maintain a high degree of system integrity.

•The 80286 provides 16 megabytes of physical address space to support today's application require- ments. This large physical memory enables the 80286 to keep many large programs and data struc- tures simultaneously in memory for high-speed access.

•For applications with dynamically changing memory requirements, such as multiuser business systems, the 80286 CPU provides on-chip memory management and virtual memory support. On an 80286-based system, each user can have up to a gigabyte (230 bytes) of virtual-address space. This large address space virtually eliminates restrictions on the number or size of programs that may be part of the system.

•Large multiuser or real-time multitasking systems are easily supported by the 80286. High~perform­ ance features, such as a very high-speed task switch, fast interrupt-response time, inter-task protec- tion, and a quick and direct operating system interface, make the 80286 highly suited to multiuser/ multitasking applications.

•The 80286 has two operating modes: Real-Address mode and Protected-Address mode. In Real- Address mode, the 80286 is fully compatible with the 8086, 8088, 80186, and 80188 microproces- sors; all of the extensive libraries of 8086 and 8088 software execute four to six times faster on the 80286, without any modification.

•In Protected-Address mode, the advanced memory management and protection features of the 80286 become available, without any. reduction in performance. Upgrading 8086 and 8088 application programs to use these new memory management and protection features usually requires only reassembly or recompilation (some programs may require minor modification). This compatibility

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