There may have been an advanced BASIC or something on
a cartridge, but I
think the ROM BASIC was in the M/B's ROM.
There was a pretty simple version of BASIC on the motherboard. The
Advanced (Extended?) BASIC cartridge brought it to the level of the
cassette BASIC on the old PC and XT.
You need the cartridge to be able to use PC-DOS BASIC or BASICA.
<<<John>>>