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=0BH, AL=00H
Set Debug Watchpoint
AX = 0B00H BX:CX = linear address of watchpoint DL = size of watchpoint (1, 2, or 4 bytes) DH = type of watchpoint
if function successful Carry flag = clear BX = watchpoint handle if function unsuccessful Carry flag = set AX = error code 8016H too many breakpoints 8021H invalid value (in DL or DH) 8025H invalid linear address (linear address not mapped or alignment error)
Sets a debug watchpoint at the specified linear address.
Under DPMI 1.0, the handle will be in the range 0-14. Under DPMI 0.9, the handle range is not limited.
The watchpoint handle corresponds to the bit number in the Virtual DR6 returned in the exception frame (see Int 31H Function 0212H and page 18 of the DPMI spec).
Text based on http://www.delorie.com/djgpp/doc/dpmi/