Intel 80286 User Manual

PROTECTION
TASK C
G3010B
Figure 7-6. Code and Data Segments Assigned to a Privilege Level
This is just one example of protection mechanism usage. Levels 1 and 2 may be used in many different
ways. The usage (or non-usage)
is up to the system designer.
Programs
at each privilege level are isolated from programs at outer layers, yet cannot affect programs
in inner layers. Programs written for each privilege level can be smaller, easier to develop, and easier
to maintain than a monolithic system where all system software can affect all other system software.
7.3.2 Privilege Usage
Privilege applies to tasks and three types of descriptors:
1. Main memory segments
2. Gates (control descriptors for state or task transitions, discussed in sections 7.5.1, 7.5.3, 8.3, 8.4
and 9.2)
3. Task state segments (discussed in Chapter 8).
7-9
pcjs.org

Intel 80286 Specifications

General

Processor Type	Microprocessor
Clock Speed	6 MHz to 25 MHz
Transistor Count	134, 000
Addressable Memory	16 MB
Instruction Set	x86
Architecture	x86
Data Bus Width	16-bit
Address Bus Width	24-bit
Operating Modes	Real mode, Protected mode
Process Technology	1.5 µm
Voltage	5V
Introduced	1982
Package	68-pin PGA