Final answer:
The typical memory device used for a computer's motherboard BIOS is EEPROM, which allows for electric reprogramming and updating directly on the motherboard.
Step-by-step explanation:
The type of memory device usually used to contain a computer's motherboard BIOS is EEPROM (Electrically Erasable Programmable Read-Only Memory). Unlike PROM (Programmable Read-Only Memory) or EPROM (Erasable Programmable Read-Only Memory), EEPROM can be reprogrammed and erased electrically without having to remove the chip from the motherboard. This feature is useful for updating the BIOS software without needing to replace the physical chip.