INT 2F - EXTENDED MEMORY SPECIFICATION (XMS) - INSTALLATION CHECK
AX = 4300h
Return: AL = 80h XMS driver installed
AL <> 80h no driver
Notes:  XMS gives access to extended memory and noncontiguous/nonEMS memory
above 640K
this installation check DOES NOT follow the format used by other
software

See also: 2F4310

2F4300 - EXTENDED MEMORY SPECIFICATION (XMS) - INSTALLATION CHECK