Consider a virtual memory system that can address a total of 232 bytes. You have unlimited hard drive space, but are limited to only 8 MB of semiconductor (physical) memory. Assume that virtual and physical pages are each 4 KB in size.
(a) How many bits is the physical address?
(b) What is the maximum number of virtual pages in the system?
(c) How many physical pages are in the system?
(d) How many bits are the virtual and physical page numbers?
(e) Suppose that you come up with a direct mapped scheme that maps virtual pages to physical pages. The mapping uses the least significant bits of the virtual page number to determine the physical page number. How many virtual pages are mapped to each physical page? Why is this “direct mapping” a bad plan?
(f) Clearly, a more flexible and dynamic scheme for translating virtual addresses into physical addresses is required than the one described in part (e). Suppose you use a page table to store mappings (translations from virtual page number to physical page number). How many page table entries will the page table contain?
(g) Assume that, in addition to the physical page number, each page table entry also contains some status information in the form of a valid bit (V) and a dirty bit (D). How many bytes long is each page table entry? (Round up to an integer number of bytes.)
(h) Sketch the layout of the page table. What is the total size of the page table in bytes?