Computers that use virtual memory do not implement virtual memory in software, which would be unbearably slow. Instead, they put extra gates and circuits on the chip to do the dynamic address translation. In some older units, the circuitry to do this was put on a separate chip called the MMU, or Memory Management Unit. Nowadays, it is more common to bundle the MMU in with the ALU and registers on the main processing chip.

A more interesting question is where the page table resides. As we shall see in the next section, there are ways of making dynamic address translation go faster on average. But it still helps if the page table lookup is very fast.