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.

2021/08/05 12:15 · prokushev

Int 31H, AH=07H, AL=03H




Discard Page Contents


AX = 0703h
BX:CX = starting linear address of pages to discard
SI:DI = size of region to discard (bytes)


if function successful
Carry flag = clear

if function unsuccessful
Carry flag = set
AX = error code
8025H	invalid linear address (range unallocated)


Discards the entire contents of a given linear memory range. This function is used when a memory object (such as a data structure) that occupies a given area of memory is no longer needed, so that the area will not be paged to disk unnecessarily. The contents of the discarded region will be undefined.

Partial pages and locked pages will not be discarded.

See also


Process manager INT 2FH 1680H, 1687H
Memory manager
Misc INT 2FH 1686H, 168AH
2021/08/13 16:23 · prokushev

en/docs/dpmi/api/int31/07/03.txt · Last modified: 2021/08/27 08:11 by prokushev