Int 14 Fn 09  - Mbbios - Get/set Options                                   [S]

   AH = 09h
   AL = option byte (see below)
   DX = port number???

Return: AL = old option byte

See Also: AH=00h"MBBIOS",AH=04h"MBBIOS",AH=10h"FOSSIL"

Bitfields for option byte:
 bit 0 transmit buffering enabled
 bit 2 hardware handshaking enabled
 bit 5 high-speed option enabled (see AH=00h"MBBIOS")
 other bits reserved