There are three drives:

    A:      %srcdrv%
    Q:      %ramdrv%
    T:      %cddrv%

The boot process is generally:

    a:\autoexec.bat
    a:\bin\modboot.cab!\bin\modboot.bat         q:\bin\modboot.bat
    a:\level3\autorun3.cab!\autorun.bat
    a:\level3\autorun3.cab!\bin\ubcd.bat        q:\bin\ubcd.bat
    (whatever the main program specified in t:\ubcd\dosapps\ubcd.ini is)