Note: This API calls are shared between DOS and Win16 personality.

DOSX is a specialized version of DPMI. Windows standard and extended mode kernel is a DPMI client app. Standard and extended mode kernel differs minimally and shares common codebase. Standard mode is just DPMI client, exnhanced mode is DPMI client running under Virtual Machime Manager. 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 provides Version 1.0 DPMI support, but reported as 0.9.

2021/08/05 12:15 · prokushev

Int 31H, AH=04H, AL=00H




Get Version


AX = 0400H


Carry flag = clear (this function always succeeds)
AH = DPMI major version as a binary number
AL = DPMI minor version as a binary number
BX = flags
Bits Significance
0 0 = host is 16-bit DPMI implementation 1 = host is 32-bit (80386) DPMI implementation
1 0 = CPU returned to Virtual 86 mode for reflected interrupts 1 = CPU returned to real mode for reflected interrupts
2 0 = virtual memory not supported 1 = virtual memory supported
3 reserved, for historical reasons
4-15 reserved for later use
CL = processor type
Value Significance
02H 80286
03H 80386
04H 80486
05H-FFH reserved for future Intel processors
DH = current value of virtual master PIC base interrupt
DL = current value of virtual slave PIC base interrupt


Returns the version number of the DPMI Specification implemented by the DPMI host. Clients can use this information to determine which function calls are supported in the current environment.

Under DPMI hosts, the major version number is returned in AH and the minor version number is returned in AL. There are two decimal digits for the minor version number with the least-significant digit representing the revision number of the minor version number. Under DPMI version 0.9 hosts, AH is returned as 0, and AL is returned as decimal 90 (5AH). In hypothetical DPMI version 2.3, AH would be returned as 2 and AL would be returned as 30 (1EH).

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/int31/04/00.txt · Last modified: 2021/08/27 05:59 by prokushev