The word is motherboard. That gender-neutral BS gets old...
...talk about irritable.....
This is hardly worth commenting on. Nevertheless, "mainboard" more accurately describes that piece of equipment than does "motherboard".
Below is an example where it makes linguistic sense:
A mothership is a vessel or aircraft that carries a smaller vessel or aircraft that operates independently from it. Examples include bombers converted to carry experimental aircraft to altitudes where they can conduct their research, or ships that carry small submarines to an area of ocean to be explored. The mothership may also recover the smaller craft, or may go its own way after releasing it.
It seems like the guys who made up this kind of terminology were being cowboys who liked to use colorful or harsh terms. Like "master" and "slave" drives, which really doesn't describe the relationship between the two drives.
Sorry to veer from the thread. Commendations to the initial poster for being industrious enough to mod his equipment and test it.