Question

1. Consider a simple paging system with the following parameters: 232 bytes of physical memory; page size of 210 bytes; 216 pages of logical address space. How many bits are in a logical address? How many bytes are in a frame! How many bits in the physical address specify the frame? How many entries are in the page table? How many bits are in each page table entry? Assume each page table entry contains a valid/invalid bit. 2. Consider a simple segmentation system that has the following segment table: Starting Address Length (bytes) 660 248 1752 422 198 996 604 For each of the following logical addresses, determine the physical address or indicate if a segment fault occurs: 0, 198 2,156 1, 530 3, 444 0,222

Answer 1

1)

Consider the following data: Size of physical memory- 2 bytes Size of page 2o bytes Number of pages in logical address space 2 bytes The number of bytes in logical address space is calculated as follows: Number of bytes inlogical address- Pages inlog ical address spacex Page size 216x210 226 bytes Thus, the number of bits in logical address is 26. The size of the frame is same as size of the page 2° bytes . The memory in the physical memory is divided into fixed sized blocks called Page frames . Each process in the logical memory is divided into fixed sized chunks called Pages. *The pages are assigned to available fixed sized blocks called Page frames The number of frames in physical memory is calculated as follows: Size of the physical memory Size of the page frame 232 1a

So, the number of bits required to specify the frame location in physical memory is 22. The number of entries in the page table is the number ofpages in the virtual memory. So, the number of entries in the page table is 216 .The number of bits required to specify the frame location in physicalmemory is 22. So, the number of bits in each page table entry is 22. .When the page table entry includes valid/invalid bit, the number of bits in each page table entry is 22+1 -23 bits

2)

To determine physical address, perform the following operations: First compare offset address with segment length. . If offset address is less than segment length, then add the starting segment address and offset address for physical address. Physical address-Starting Address +Offset address Otherwise, it occurs segment fault.

Consider the following logical address is (0,198) From this logical address, offset address is 198, segment number is 0, starting address is 660 and segment length is 248. Now check the condition (offset address segment length) that is (198 < 248) Yes it's true. So add the starting address and offset address for physical address. Physical address - Starting Address + offset address = 660 + 198 -858 Theretore, the Physical aodress tor tis logcal aodres is 858.

Consider the following logical address is (2,156) From this logical address, offset address is 156, segment number is 2, starting address is 222 and segment length is 198. Now check the condition (offset address segment length) that is (156 < 198) Yes it's true. So add the starting address and offset address for physical address. Physical address - Starting Address + offset address -222 +156 - 378 Therefore, the Physical address for this logical address is 378

Consider the following logical address is (1.530) From this logical address, offset address is 530, segment number is 1, starting address is 1752 and segment length is 422 Now check the condition (offset address <segment length) that is (530< 422 Condition is false. So it occurs segment fault. Therefore, the segment 1 has a length of 422 bytes, it occurs segment fault.

Consider the following logical address is (3,444). From this logical address, offset address is 444 segment number is 3, starting address is 996 and segment length is 604. Now check the condition (offset address <segment length) that is (444 < 604 Yes it's true. So add the starting address and offset address for physical address. Physical address - Starting Address + offset address = 996 + 444 1440 Therefore, the Physical address for this logical address is 1440

Consider the following logical address is (0,222) From this logical address, offset address is 222 segment number is 0, starting address is 660 and segment length is 248. Now check the condition (offset address segment length) that is (222 < 248) Yes it's true. So add the starting address and offset address for physical address. Physical address - Starting Address + offset address 660 222 = 882 Therefore, the Physical address for this logical address is 882.