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Unformatted text preview: CHAPTER 4 Memory Management ——® given control of the CPU, the operating system must set the page table registers appropriately for the process. Q: In each of the listed wgry management schemes. briefly describe the functions ' performed by the Mimanagement hardware! (a) Single Absolute Partition (with base register) (b) Multiple Variable Partitions (c) Buddy System (‘3) Simple Paging Answer: (a) Single Absolute Partition (with base register) Each time a memory location is referenced, its address is compared to the addressinfltebaseregistenAnaddresssmalierthanthenddressinthebase register results in a memory-fault trap. Multiple Variable Partitions Each time a memory location is referenced, its logical address is compared to the address in the size register. An address larger than the address in the size register results in a “cry-fault trap. The logical address is also added to the address in the relocation register to generate the memory location‘s physical address. Buddy System The hardware for the buddy system works the same way as the hardware for multiple variable partitions. Simple Paging Each time a memory location is referenced. the paging hardware translates the logical address into the physical address. The page number bits in the logical address are used as an index into the page table. The logical address page offset bits are appended to the page frame number, obtained floor the appropriate page table entry, to form the physical address. A program containing relocatable code was crowd, assuming it would be loaded at address 0. In its code, the program refers to the following addresses: 50, 78, 150, 152, 154. If the program is loaded into memory starting at location 250. how do those addresses have to be adjusted? _" T , 4 Answer: All addresses need to be adjusted upward by 250. So the adjusted addresses would be 300, I328, 409, 402, and 404. {IQ-f"! 5n- _'_‘_' 1‘ 'f 4.4 How is an absolute partition scheme using relocatable code similar to a relocatabie partition scheme? How are they difi'erent? ...
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