Note: This API calls are shared between DOS and Win16 personality.
DPMI is a shared interface for DOS applications to access Intel 80286+ CPUs services. DOS DMPI host provides core services for protected mode applications. Multitasking OS with DOS support also provides DMPI in most cases. Windows standard and extended mode kernel is a DPMI client app. Standard and extended mode kernel differs minimally and shares common codebase. Standard Windows kernel works under DOSX extender. DOSX is a specialized version of 16-bit DPMI Extender (but it is standard DPMI host). Standard mode is just DPMI client, exnhanced mode is DPMI client running under Virtual Machime Manager (really, multitasker which allow to run many DOS sessions). Both modes shares DPMI interface for kernel communication. The OS/2 virtual DOS Protected Mode Interface (VDPMI) device driver provides Version 0.9 DPMI support for virtual DOS machines. Win16 (up to Windows ME) provides Version 0.9 DPMI support.
DPMI host often merged with DPMI extender. Usually DPMI extender provide DPMI host standard services and DOS translation or True DPMI services.
Int 31H, AH=02H, AL=13H
Set Extended Processor Exception Handler Vector (Real Mode)
AX = 0213H BL = exception/fault number (00H-1FH) CX:(E)DX = selector:offset of exception handler
if function successful Carry flag = clear if function unsuccessful Carry flag = set AX = error code 8021H invalid value (BL not in range 00H-1FH) 8022H invalid selector
CX:(E)DX does not specify a real-mode segment:offset. The reason is that this function allows a client to set the address of an exception handler which will receive control in protected mode when the specified exception occurs in real mode (i.e. the host will provide an implied mode switch for the purposes of servicing the exception, then return to real mode after the handler exits).
Real mode exceptions are sent to the primary client of the virtual machine. (See Appendix A: Glossary for definition of primary client.)
Refer to the rules for descriptor usage in Appendix D.
Text based on http://www.delorie.com/djgpp/doc/dpmi/