INT 2F - DOS 5.0 - QUERY FREE HMA SPACE
AX = 4A01h
Return: BX = number of bytes available in HMA (0000h if DOS not using HMA)
ES:DI -> start of available HMA area (FFFFh:FFFFh if not using HMA)
Note:   called by Windows 3.1 DOSX.EXE
SeeAlso: AX=4A02h

See also: 2F4310

2F4A01 - DOS 5.0 - QUERY FREE HMA SPACE