ROM vs memory board

ROM and memory board both are nouns.

Word	Noun	Adjective	Verb	Adverb
ROM	Yes	No	No	No
memory board	Yes	No	No	No

As nouns, memory board is a hypernym of ROM; that is, memory board is a word with a broader meaning than ROM:

ROM: (computer science) memory whose contents can be accessed and read but cannot be changed
memory board: an electronic memory device

Other hypernyms of ROM include computer memory, computer storage, memory, storage, store.

ROM (noun)	memory board (noun)
(computer science) memory whose contents can be accessed and read but cannot be changed	an electronic memory device