Two Levels To One Byte
A machine has a 14-bit virtual address space, 64-byte pages and 4-byte page table entries, so the VPN is 8 bits and the offset is 6 bits. The two-level table splits the VPN evenly: the top 4 bits index the page directory, the next 4 bits index the page of the page table.
Page directory (16 entries):
| index | valid | PFN |
|---|---|---|
| 0 | 1 | 44 |
| 1-2 | 0 | - |
| 3 | 1 | 88 |
| 4-14 | 0 | - |
| 15 | 1 | 91 |
Page of the page table living in PFN 88 (16 entries):
| index | valid | prot | PFN |
|---|---|---|---|
| 0-4 | 0 | - | - |
| 5 | 1 | rw- | 27 |
| 6 | 1 | r-x | 12 |
| 7-15 | 0 | - | - |
A load is issued to virtual address 0x0D5A. What physical address does the hardware form?
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