About MMU (Memory Management Unit)?

Question

the MMU compares the incoming (virtual) address to the limit register, causing a fault if it is too large. An alternative design would be to first add the virtual address to the base register and then compare the result to the (physical) address in the limit register. Are the two methods logically equivalent? Are they equivalent in performance?

Answer 1

Clearly, they are NOT logically equivalent, since in the latter case, the "base" register have a great impact on the eval. And even you said, one is comparing virtual to virtual limit, and the other is physical to physical limit.

The latter uses two operations (add, and compare), whereas the former use a single compare.