Romident 'sub' region

[big10p]

I've identified the purpose of all ROMs on a board, except one that romident says is 'sub' region. Pretty sure this ROM is for sound. Just wondering why it's labelled as 'sub'?

 

[favouredson]

MAME generally refers to the sound or second CPU as the sub CPU.
Romident uses the info from MAME.
Mystery solved.

 

[big10p]

Thanks for confirming.