"From a developer's point of view, the 68000 provides a full suite of 32-bit operations but has a 16-bit external data bus and is implemented using a 16-bit arithmetic logic unit, so 32-bit computations are transparently handled as multiple 16-bit values at a performance cost. Also, while addresses are 32-bit, the chip is limited to 16 MB of physical memory using the lower 24 of the address bits.[35][36] The later Amiga 2500, Amiga 3000, Amiga 4000 and Amiga 1200 models use fully 32-bit, 68000-compatible processors from Motorola with improved performance and larger addressing capability."

https://en.wikipedia.org/wiki/Amiga