Old Big Core is a giant Big Core MK I that appears in Otomedius Excellent. It is not known if it has a pilot. One of its laser cannons on the front shoots down Meta Lium's Big Core DX before the player makes their approach. When the player reaches the laser cannon, it fires off to the side before Old Big Core moves and floats most of the way out of the water.
To fight Old Big Core, the player heads inside the path left open because there are no solid barriers impeding forward progress. As it turns out, the inside of Old Big Core is a Gunwall situated in front of the actual, full-size core to the ship. There are two smaller mini-cores, one on either side of the central, not-so-mini core which is about as big as the player is tall (if not a little bigger). The top and bottom edges of the three leftmost barrier sections have turrets, and together will fire a concussive laser to restrict movement, then each fire a normal shot at the player. To prevent the concussive laser attack, take out either side of each pair. The main threat, however, is the moving turret on the final barrier section's rail that moves up and down with the player and fires two rows of normal shots. Sacrificing a hit on the force field to move past and get behind this moving turret gun is the best option for destroying the gunwall's three cores; destroying the weapon is not advised unless the player needs to do so in order to obtain a weapon card in a certain loop and difficulty.