The X 86 Microprocessors: Architecture, Programming and Interfacing (8086 to Pentium) 2nd Edition by Pearson

14-38

THE

x86 MICROPROCESSORS

ii) The context of the current task is saved, i.e., contents of the registers are copied to

the TSS. The EIP register, which is now stored in the TSS, will be pointing to the

next instruction after the one that caused the task switch. These actions correspond

to ‘saving the context’ of the abandoned task.

iii) Next, the actions for taking up the new task are begun. The Task Register (TR) is

loaded with the new task’s selector. The selector is either the operand of a control

transfer instruction or is taken from a task gate, which gets the TSS descriptor and

then the TSS from memory.

iv) Now the new task can be proceeded with. For that, its state is loaded from the TSS

into the corresponding registers. The registers ...