IBM Professional Series User Manual page 342

Diagnose Instruction in VMjPC
The DIAGNOSE instruction cannot be used in a virtual
machine for its normal function. If a virtual machine
attempts to execute a DIAGNOSE instruction, a program
interrupt returns control to CPo Since a DIAGNOSE
instruction issued in a virtual machine results only in
returning control to CP and not in performing normal
DIAGNOSE functions, the instruction is used for
communication between a virtual machine and CPo
The machine language format of DIAGNOSE is:
~<------
4 bytes
------~)
I
83
I
Rx
I
Ry
I
CODE
Where:
83
is X'83' and interpreted by the assembler as the
DIAGNOSE instruction.
Note: There is no assembler mnemonic for DIAGNOSE.
Rx,Ry
are general purpose registers that contain operand
storage addresses or return codes passed to the
DIAGNOSE interface.
CODE
is a two-byte hexadecimal value that CP uses to
determine what DIAGNOSE function to perform. The
codes defined for the VM/PC user are described in this
section.
Because DIAGNOSE operates differently in a virtual
machine than it does in a real machine, a program should
determine that it is operating in a virtual machine before
issuing a DIAGNOSE instruction, and prevent execution of a
DIAGNOSE when in a real machine. The Store Processor
ID (STIDP) instruction provides a program with information
about the processor in which it is executing, including the
Appendix A. CP/CMS Interface A-3