MultiChips use multiple silicon dies interconnected within one chip package. These types of chips are more common in military and space applications where a smaller form factor is required, or where the silicon dies must be protected from radiation. The pictures below are of MultiChips with the lids of the chips removed. In space, and some military applications, the metal "box" around the chip structure would be radiation hardened to resist malfunction due to radiation exposure.

Click the pictures for larger views