INT 13 - SWBIOS - INSTALLATION CHECK
AH = F9h
DL = drive number (80h,81h)
Return: CF clear
DX = configuration word
bit 15 set if other SWBIOS extensions available
CF set on error
Note:   SWBIOS is a TSR by Ontrack Computer Systems; Disk Manager also supports
these calls

See also: 13EE

13F9 - SWBIOS - INSTALLATION CHECK