Int 15 Fn E4  - Tandy??? - ???                                             [b]

   AH = E4h
   AL = subfunction
       21h, 89h, 8Ah, 8Bh called by 386MAX v6.01
   DL = ???

Return: DL = 00h if successful???

Note:  the section of code in 386MAX which calls these functions also checks
     whether the ROM BIOS has both Tandy and Phoenix Technologies
     signatures if these calls fail; the Tandy 1000SL/TL BIOS does not
     support this function, however, returning the usual CF set/AH=86h for
     "unsupported function".