Discussion
Consider a demand paging memory management system with 32-bit logical address, 20-bit physical address, and page size of 2048 bytes. Assuming that the memory is byte addressable, what is the maximum number of entries in the page table?
Answer: A
The maximum number of page table entries is \(2^{21}\).
A single-level page table needs one entry for each page of the logical address space. The page size is \(2048 = 2^{11}\) bytes, so 11 of the 32 logical address bits are the offset within a page:
\[ \text{entries} = \frac{2^{32}}{2^{11}} = 2^{21} \]
The 20-bit physical address decides the number of frames, \(2^{20}/2^{11} = 2^{9}\), and the width of each entry, but not how many entries there are. \(2^{20}\) wrongly takes the physical address width, and \(2^{22}\) and \(2^{24}\) assume smaller pages.
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