Internally, it uses a 16-bit data arithmetic logic unit (ALU) and two more 16-bit ALUs used mostly for addresses. At one time, one 32-bit address and one 16-bit data calculation can take place within the MC68000. This speeds instruction execution time considerably by processing addresses and data in parallel.
== Data and Address Buses ==
Externally, the processor uses a 16‑bit data bus, so memory accesses occur in 16‑bit (word) units, though it supports byte accesses via data strobes.
The address bus is 24 bits wide; while internal address computations occur using 32‑bit arithmetic, only the lower 24 bits are available on the physical pins.
This design yields a flat memory model with a maximum addressable space of 16 MB without the complications of segmentation, simplifying both operating system design and application programming.
But this gave trouble with later CPU models as it was a common trick for programs to store data in the 4th byte of an address (which simply would be ignored).
== Register Structure ==