Intel ARCHITECTURE IA-32 User Manual Page 246

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6-4 Vol. 3A
TASK MANAGEMENT
Use of task management facilities for handling multitasking applications is optional. Multi-
tasking can be handled in software, with each software defined task executed in the context of
a single IA-32 architecture task.
6.2 TASK MANAGEMENT DATA STRUCTURES
The processor defines five data structures for handling task-related activities:
Task-state segment (TSS).
Task-gate descriptor.
TSS descriptor.
Task register.
NT flag in the EFLAGS register.
When operating in protected mode, a TSS and TSS descriptor must be created for at least one
task, and the segment selector for the TSS must be loaded into the task register (using the LTR
instruction).
6.2.1 Task-State Segment (TSS)
The processor state information needed to restore a task is saved in a system segment called the
task-state segment (TSS). Figure 6-2 shows the format of a TSS for tasks designed for 32-bit
CPUs. The fields of a TSS are divided into two main categories: dynamic fields and static fields.
For information about 16-bit Intel 286 processor task structures, see Section 6.6, “16-Bit Task-
State Segment (TSS).” For information about 64-bit mode task structures, see Section 6.7, “Task
Management in 64-bit Mode.”
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