INT 2F - Novell DOS Protected Mode Services (DPMS) - INSTALLATION CHECK
        AX = 43E0h
Return: AX = 0000h if installed
            ES:BX -> registration structure (see below)
Note:   this specification is still in beta
SeeAlso: INT 2F/AX=1687h

Format of registration structure:
Offset  Size    Description
 00h    DWORD   real-mode API entry point
 04h    DWORD   16-bit protected-mode API entry point
 08h  8 BYTEs   reserved (0)
 10h  8 BYTEs   blank-padded server OEM name
 18h    WORD    flags
                bit 0: fast processor reset available (286 only)
                bits 1-15 reserved (undefined)
 1Ah  2 BYTEs   DPMS version (major,minor)
 1Ch    BYTE    CPU type (02h = 286, 03h = 386 or higher)

Call DPMS entry point with:
        AX = 0100h call protected-mode procedure
                CX = number of words of stack to copy
                ES:DI -> callup/down register structure (see below)
                Return: CF clear if successful
                        CF set on error
                            AX = error code (see below)
        AX = 0101h call real-mode procedure (RETF return)
                CX = number of words of stack to copy
                ES:DI -> callup/down register structure (see below)
                Return: CF clear if successful
                        CF set on error
                            AX = error code (see below)
        AX = 0102h call real-mode procedure (IRET return)
                CX = number of words of stack to copy
                ES:DI -> callup/down register structure (see below)
                Return: CF clear if successful
                        CF set on error
                            AX = error code (see below)
        AX = 0103h call real-mode interrupt handler
                BL = interrupt number
                CX = number of words of stack to copy
                ES:DI -> callup/down register structure (see below)
                Return: CF clear if successful
                        CF set on error
                            AX = error code (see below)
        AX = 0200h allocate descriptors
                CX = number of descriptors to allocate
                Return: CF clear if successful
                            AX = first descriptor allocated
                        CF set on error
                            AX = error code (see below)
        AX = 0201h free a descriptor
                BX = descriptor
                Return: CF clear if successful
                        CF set on error
                            AX = error code (see below)
        AX = 0202h create alias descriptor
                BX = descriptor
                Return: CF clear if successful
                            AX = alias descriptor
                        CF set on error
                            AX = error code (see below)
        AX = 0203h build alias to real-mode segment
                BX = descriptor
                CX = real-mode segment
                Return: CF clear if successful
                        CF set on error
                            AX = error code (see below)
        AX = 0204h set descriptor base
                BX = descriptor
                CX:DX = base address
                Return: CF clear if successful
                        CF set on error
                            AX = error code (see below)
        AX = 0205h set descriptor limit
                BX = descriptor
                CX = limit
                Return: CF clear if successful
                        CF set on error
                            AX = error code (see below)
        AX = 0206h set descriptor type/attribute
                BX = descriptor
                CL = type
                CH = attribute
                Return: CF clear if successful
                        CF set on error
                            AX = error code (see below)
        AX = 0207h get descriptor base
                BX = descriptor
                Return: CF clear if successful
                            CX:DX = base address
                        CF set on error
                            AX = error code (see below)
        AX = 0300h get size of largest free block of memory
                Return: CF clear if successful
                            BX:CX = size
                        CF set on error
                            AX = error code (see below)
        AX = 0301h allocate block of extended memory
                BX:CX = size
                Return: CF clear if successful
                            BX:CX = base address
                            SI:DI = handle
                        CF set on error
                            AX = error code (see below)
        AX = 0302h free block of extended memory
                SI:DI = handle
                Return: CF clear if successful
                        CF set on error
                            AX = error code (see below)
        AX = 0303h map linear memory
                ES:[DI] = DDS
                Return: CF clear if successful
                            BX:CX = base address
                            SI:DI = handle
                        CF set on error
                            AX = error code (see below)
        AX = 0304h unmap linear memory
                SI:DI = handle
                Return: CF clear if successful
                        CF set on error
                            AX = error code (see below)
        AX = 0400h relocate segment to extended memory
                ES:SI = base address
                CX = limit
                BL = type
                BH = attribute
                DX = selector or 0000h
                Return: CF clear if successful
                            AX = selector
                            BX:CX = new base address
                            SI:DI = handle
                        CF set on error
                            AX = error code (see below)

Values for error code:
 8000h  general error
 8001h  unsupported function
 8011h  descriptor unavailable
 8012h  linear memory unavailable
 8013h  physical memory unavailable
 8021h  invalid value
 8022h  invalid selector
 8023h  invalid handle

Format of callup/down register structure:
Offset  Size    Description
 00h    DWORD   EDI
 04h    DWORD   ESI
 08h    DWORD   EBP
 0Ch  4 BYTEs   reserved (0)
 10h    DWORD   EBX
 14h    DWORD   EDX
 18h    DWORD   ECX
 20h    DWORD   EAX
 24h    DWORD   EIP
 28h    WORD    CS
 2Ah  2 BYTEs   reserved (0)
 2Ch    DWORD   EFLAGS
 30h    DWORD   ESP
 34h    WORD    SS
 36h  2 BYTEs   reserved (0)
 38h    WORD    ES
 3Ah  2 BYTEs   reserved (0)
 3Ch    WORD    DS
 3Eh  2 BYTEs   reserved (0)
 40h    WORD    FS
 42h  2 BYTEs   reserved (0)
 44h    WORD    GS
 46h  2 BYTEs   reserved (0)

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