16.2.4 Building the MMU
There are three architectural parameters that characterize a virtual memory system and hence the architecture of the MMU. P is the number of address bits used for the page offset in both virtual and physical addresses. V is the number of address bits used for the virtual page number. And M is the number of address bits used for the physical page number. All the other parameters, listed on the right, are derived from these three parameters. As mentioned earlier, the typical page size is between 4KB and 16KB, the sweet spot in the tradeoff between the downside of using physical memory to hold unwanted locations and the upside of reading as much as possible from secondary storage so as to amortize the high cost of accessing the initial word over as many words as possible. The size of the virtual address is determined by the ISA. We're now making the transition from 32-bit architectures, which support a 4 gigabyte virtual address space, to 64-bit architectures, which supp...