INT 2F - DOS Protected-Mode Interface - INSTALLATION CHECK
AX = 1687h
Return: AX = 0000h if installed
BX = flags
bit 0: 32-bit programs supported
CL = processor type (02h=80286, 03h=80386, 04h=80486)
DH = DPMI major version
DL = two-digit DPMI minor version
SI = number of paragraphs of DOS extender private data
ES:DI -> DPMI mode-switch entry point
AX nonzero if not installed
SeeAlso: INT 38/AH=10h

Call mode switch entry point with:
AX = flags
bit 0: set if 32-bit program
ES = real mode segment of buffer for DPMI private data (ignored if
SI was zero)
Return: CF set on error
program still in real mode
AX = error code (DPMI 1.0+)
8011h unable to allocate all necessary descriptors
8021h 32-bit program specified, but 16-bit DPMI host
CF clear if successful
CS = 16-bit selector corresponding to real-mode CS
SS = selector corresponding to real-mode SS (64K limit)
DS = selector corresponding to real-mode DS (64K limit)
ES = selector to program's PSP (100h byte limit)
FS = GS = 0
high word of ESP = 0 if 32-bit program
program now in protected mode
Note:   this entry point is only called for the initial switch to protected
mode

See also: 2F1686

2F1687 - DOS Protected-Mode Interface - INSTALLATION CHECK