Int 15 Fn 53B0  - Intel System Management Bus - Real Mode Connect          [X]

   AX = 53B0h
   BH = 02h
   CX = 6941h ('iA')

Return: CF clear if successful
       AX = SMBus Real mode code segment
       BX = offset of entry point into SMBus BIOS Interface
       CX = SMBus Real mode data segment
   CF set if error
       AH = error code (01h,02h,0Ah,86h) (see #0410)
       AL = sub-error code if error code is 02h (see #0411)
Desc:  connect to SMBus interface; once connected, all SMBus calls are made
     to the supplied entry point instead of INT 15 (with registers
     identical to those described here for INT 15)

Notes: Support for this function is optional
   this function is only supported in INT 15 mode when implemented

See Also: AX=53B0h/BH=01h,AX=53B0h/BH=03h,AX=53B0h/BH=04h,AX=53B0h/BH=05h