INT 14 - MBBIOS - WRITE BUFFER
        AH = 0Ah
        CX = count
        ES:DI -> buffer
Return: AX = status (see AH=03h)
        CX = unsent character count
        DI updated
Note:   the PACCOM version of MBBIOS does not use CX or ES:DI; instead, ES
          contains the segment of a buffer containing the packet to be sent,
          which by default will be freed once the packet has been sent.  Use
          AH=0Ch"MBBIOS" to allocate the buffer.
SeeAlso: AH=01h,AH=0Bh"MBBIOS",AH=0Ch"MBBIOS",AH=19h"FOSSIL"

Format of PACCOM buffer:
Offset  Size    Description
 00h 504 BYTEs  data area
1F8h    WORD    length of data in data area
1FAh    BYTE    flags/status
                bit 7: don't discard buffer after transmitting data
                bit 6: buffer has been transmitted
1FBh    BYTE    reserved (0) for additional flags/status
1FCh    WORD    user data
1FEh    WORD    MBBIOS-internal pointer to next buffer

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