INT 21 - FlashTek X-32VM - GET SYSTEM SEGMENTS AND SELECTORS
        AX = 2509h
Return: CF clear
        EAX high word = default DS
        AX = alias for 16-bit data segment
        BX = real mode code segment
        EDX high word = selector covering full 4GB address space
        DX = default SS
        ESI high word = PSP selector
        SI = environment selector