4.2 Systems Instructions

Systems instructions deal with such functions as:

  1.  Verification of pointer parameters (refer to Chapter 6):

    ARPL             -- Adjust RPL
    LAR              -- Load Access Rights
    LSL              -- Load Segment Limit
    VERR             -- Verify for Reading
    VERW             -- Verify for Writing

  2.  Addressing descriptor tables (refer to Chaper 5):

    LLDT             -- Load LDT Register
    SLDT             -- Store LDT Register
    LGDT             -- Load GDT Register
    SGDT             -- Store GDT Register

  3.  Multitasking (refer to Chapter 7):

    LTR              -- Load Task Register
    STR              -- Store Task Register

  4. Coprocessing and Multiprocessing (refer to Chapter 11):

    CLTS             -- Clear Task-Switched Flag
    ESC              -- Escape instructions
    WAIT             -- Wait until Coprocessor not Busy
    LOCK             -- Assert Bus-Lock Signal

  5.  Input and Output (refer to Chapter 8):

    IN               -- Input
    OUT              -- Output
    INS              -- Input String
    OUTS             -- Output String

  6.  Interrupt control (refer to Chapter 9):

    CLI              -- Clear Interrupt-Enable Flag
    STI              -- Set Interrupt-Enable Flag
    LIDT             -- Load IDT Register
    SIDT             -- Store IDT Register

  7.  Debugging (refer to Chapter 12):

    MOV              -- Move to and from debug registers

  8.  TLB testing (refer to Chapter 10):

    MOV              -- Move to and from test registers

  9.  System Control:

    SMSW             -- Set MSW
    LMSW             -- Load MSW
    HLT              -- Halt Processor
    MOV              -- Move to and from control registers

In addition to the chapters cited above, detailed information about each of these instructions can be found in the instruction reference chapter, Chapter 17.