A computer system supports -bit virtual addresses as well as -bit physical addresses. Since the virtual address space is of the same size as the physical address space, the operating system designers decide to get rid of the virtual memory entirely. Which one of the following is true?
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Answer: C
When virtual memory is entirely removed, the system operates solely on physical addresses. Let's analyze the implications of this design choice:
- Address Translation: In a system with virtual memory, the CPU generates virtual addresses which must be translated into physical addresses. This translation requires dedicated hardware support, specifically the Memory Management Unit (MMU) and the Translation Lookaside Buffer (TLB).
- Eliminating Virtual Memory: If virtual memory is discarded, the CPU directly issues physical addresses to the memory bus. Since there is no longer any translation from virtual to physical addresses, the hardware mechanisms (MMU, TLB, page table walking hardware) are no longer needed.
Therefore, hardware support for memory management is no longer needed.
Analysis of other options:
- Option A: Multi-user support and protection can still be implemented using simpler hardware mechanisms (such as base and limit registers) or via software-level isolation, so it is not entirely impossible.
- Option B: Cache organization (like PIPT or VIPT) does not inherently become more efficient without virtual memory; cache design is primarily governed by latency, associativity, and block size.
- Option D: CPU scheduling algorithms (like Round Robin, SRTF, etc.) manage process execution states and are independent of the presence of virtual memory.
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