The Unabridged Pentium 4 IA32 Processor Genealogy

Linked Tasks

Under the following circumstances, a task is linked to the task that transferred execution to it (because the calling or interrupted task must be resumed when the called task has completed execution):

• If a far CALL selects a Call Gate in the GDT or the LDT, or where the CS portion of the branch target address selects a Task Gate in the GDT or the LDT, then the calling task is suspended and a task switch occurs to the called task. In the called task the execution of the IRET instruction at the end of the called procedure (when EFlags[NT] = 1) causes a switch back to the calling task and resumption of its execution at the instruction that follows the CALL instruction (note that only the IRET instruction can cause a task switch; the ...