65 votes 65 votes A computer system supports $32$-bit virtual addresses as well as $32$-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? Efficient implementation of multi-user support is no longer possible The processor cache organization can be made more efficient now Hardware support for memory management is no longer needed CPU scheduling can be made more efficient now Operating System gatecse-2006 operating-system virtual-memory normal ugcnetcse-june2012-paper3 + – Rucha Shelke asked Sep 26, 2014 recategorized Oct 23, 2018 by Pooja Khatri Rucha Shelke 25.6k views answer comment Share Follow See all 8 Comments See all 8 8 Comments reply Show 5 previous comments aryavart commented May 5, 2021 reply Follow Share @kamal250 Swap space on disk can be used without virtual memory. 1 votes 1 votes John_Smith commented Dec 10, 2023 reply Follow Share Virtual memory isn’t just a combination of swap space and main memory. It is an interface that allows for many more facilities as mentioned in the answers and comments of https://gateoverflow.in/1488/gate-cse-1999-question-2-10, https://gateoverflow.in/701/gate-cse-2001-question-1-8 and https://gateoverflow.in/1841/gate-cse-2006-question-63-ugcnet-june2012-iii-45. It’s just that one way of implementing VM is through a conjunction of main memory and swap space, and other hardware and/or software techniques. But, without VM too, we can take advantages of techniques like standard swapping/swapping (moving entire processes to and fro swap space when in paucity of physical memory), swapping with paging/paging (moving process pages instead of entire processes to and fro swap space when in paucity of physical memory), page tables, segmentation, etc. They are like individual dishes that a restaurant (OS) is serving, whereas VM is a combo pack. Ref. – Operating System Concepts (10th edition, Section 9.5.) P.S. Paging also refers to ‘a memory-management scheme that permits a process’ physical address space to be non-contiguous’, along with the one mentioned above. So, one should derive the meaning of the word based on the context it’s used in. 1 votes 1 votes PreyumKr commented Dec 21, 2023 reply Follow Share what was the gate answer for this question... 0 votes 0 votes Please log in or register to add a comment.
Best answer 99 votes 99 votes A is the best answer here. Virtual memory provides increased address space for processes memory protection relocation So, when we don't need more address space, even if we get rid of virtual memory, we need hardware support for the other two. Without hardware support for memory protection and relocation, we can design a system (by either doing them in software or by partitioning the memory for different users) but those are highly inefficient mechanisms. i.e., there we have to divide the physical memory equally among all users and this limits the memory usage per user and also restricts the maximum number of users. Arjun answered Feb 6, 2015 edited Jul 27, 2016 by Arjun Arjun comment Share Follow See all 26 Comments See all 26 26 Comments reply mcjoshi commented Sep 21, 2016 reply Follow Share @Arjun sir, I do think that (C) is the answer. Wikipedia says : 6 votes 6 votes Shubham Pandey 2 commented Oct 1, 2016 reply Follow Share pls correct your ans Arjun sir 2 votes 2 votes Arjun commented Oct 1, 2016 reply Follow Share Why? :O 1 votes 1 votes Vaishali Trivedi commented Nov 9, 2016 reply Follow Share sir virtual address space same as physical then 1 process will reside in memory then why we need protection and relocation 0 votes 0 votes Arjun commented Nov 9, 2016 reply Follow Share ^Why only 1? Then how can multiple users use the system? 2 votes 2 votes Vaishali Trivedi commented Nov 9, 2016 reply Follow Share because virtual address space is 32 bit long . 0 votes 0 votes Arjun commented Nov 9, 2016 reply Follow Share So, how multiple users use the system- actually multiple users always imply multiple processes. 3 votes 3 votes Vaishali Trivedi commented Nov 9, 2016 reply Follow Share sir ,we can use segmentation so more than 1 process can reside in main memory so multiprograming is supported it can support multiuser system . Beacuse many processes in main memory we need protection and relocation . now i am correct? 1 votes 1 votes Arjun commented Nov 9, 2016 reply Follow Share Yes, more or less. Segmentation is also a virtual memory technique. But we can statically partition the memory and give to different processes. But say with 10 jobs, we effectively reduce the memory available to 1/10th. So, for this reason they added "efficient implementation" and not just "implementation" in option A. 6 votes 6 votes Harsh181996 commented Nov 19, 2016 reply Follow Share Sir, according to your answer only if we remove hardware support along with VM , only then efficient implementation of multi-user support is not possible right ? So does that mean if option C happens only then option A will occur ? 1 votes 1 votes rajaneesh16 commented Dec 16, 2016 reply Follow Share When you are talking about the hardware support for memory management, simple paging or simple segmentation requires memory management unit(MMU) too. But this doesn't involve virtual memory. You can refer stallings on this one. Demand paging requires h/w support for efficiently implementing multi user support. Because if there is no hardware support, you got to do it by other means. Using s/w approach or partitioning memory among users on some priority or whatever would consume admin time or CPU cycles. This is clearly inefficient. a is the answer. 5 votes 5 votes Ayush Upadhyaya commented Aug 15, 2017 reply Follow Share We can also say that one of the goals of memory management is efficient utilization of memory. Compaction is a technique which helps to combat external fragmentation. And compaction is possibly only via dynamic relocation which needs hardware support of relocation registers. So, Hardware support for memory management is still needed for efficient utilization of memory. 28 votes 28 votes Manu Thakur commented Nov 6, 2017 reply Follow Share yes (A) is the best possible option here, hardware will still be needed to provide "memory protection" even in the case when PAS >= VAS. 6 votes 6 votes Kishan Singh commented Dec 7, 2017 reply Follow Share UGC itself has given C as the correct answer. Check the link given below: http://www.ugcnetonline.in/updated_keys/J2012_updatekeys/SC087_III.pdf :\ 0 votes 0 votes sushmita commented Dec 11, 2017 reply Follow Share If this question comes in any other competitive exam i am sure that they will give marks for answer C though A is correct. That's the power of copying.... :( 14 votes 14 votes Asim Siddiqui 4 commented Oct 16, 2018 reply Follow Share can I also say that option (C) is not correct because "THE USER PROGRAM NEVER SEES THE REAL PHYSICAL ADDRESSES & IT DEALS WITH LOGICAL ADDRESSES. SO THE MEMORY-MAPPING HARDWARE(MMU) CONVERTS LOGICAL ADDRESSES INTO PHYSICAL ADDRESSES"?? 0 votes 0 votes Nitesh Singh 2 commented Nov 21, 2018 reply Follow Share Option C says "hardware support for MEMORY MANAGEMENT is no longer needed" which is true. In addition to implement virtual addressing special hardware support is needed like TLB... 1 votes 1 votes DIYA BASU commented Jan 2, 2019 reply Follow Share Sir, Can we say that when Process size is greater than main memory size then process address space is called logical address space else it is called virtual address space?? 0 votes 0 votes Verma Ashish commented Apr 7, 2019 reply Follow Share NptelQ2 :( 0 votes 0 votes Arjun commented Apr 7, 2019 reply Follow Share I think some TA people are making those answers. 4 votes 4 votes Shivateja MST commented Dec 18, 2019 reply Follow Share Now can we consider the virtual address generated by CPU is same as that of Physical Address since no Virtual Memory concept is involved? Anyone please reply.. 0 votes 0 votes Abhineet Singh commented Dec 7, 2020 reply Follow Share what is the answer to this A or C? 0 votes 0 votes himanshu2021 commented Jan 16, 2021 reply Follow Share Shivateja MST No, we use dynamic loading, so the CPU can never know the physical address(even if PAS > VAS). In case of contiguous memory allocation we also perform address translation. Abhineet Singh’ Answer should be A) Hardware will still be needed for address translation(MMU). 1 votes 1 votes Sanjeev kumar Sen commented Oct 23, 2021 reply Follow Share @arjun sir if msq than a c both will be correct right 1 votes 1 votes JAINchiNMay commented Jun 30, 2022 reply Follow Share @Arjun sir, if these type of questions comes in exam then what should we do?...leave this 0 votes 0 votes Arjun commented Jun 30, 2022 reply Follow Share Why leave? Isn't the answer explained here? 1 votes 1 votes Please log in or register to add a comment.
7 votes 7 votes If there is no Virtual memory ,we cannot increase the degree of multiprogramming. so Option A) Laxmi answered Dec 25, 2014 Laxmi comment Share Follow See all 10 Comments See all 10 10 Comments reply Show 7 previous comments Ashutosh Mishra 1 commented Sep 15, 2016 reply Follow Share We are removing concept of VM not the HDD where all the programs stored So who are claiming that every thing will be in main memory are wrong since suppose if you need to load another process whose program is in HDD How would you loaded without HW support. 0 votes 0 votes vamsi2376 commented Sep 15, 2016 reply Follow Share here the question is about Hardware support for memory management. Not to load a program.... Loading a program into memory without hardware support doesn't make any sense... I.e. to make effective use of available memory using memory management techniques like demand paging... If virtual memory is not available then we don't have the advantage to run multiple programs simultaneously. But we can run programs using basic techniques like contiguous allocation, non contiguous allocation, paging and segmentation... This makes Efficient implementation of multi-user support is no longer possible would be the appropriate choice here.... 1 votes 1 votes suvasish pal commented Sep 20, 2017 reply Follow Share @ vamsi2376 where did u get this? 0 votes 0 votes Please log in or register to add a comment.
2 votes 2 votes Page 348 Stallings 6th edition In simple paging, processor uses page number, offset to calculate absolute address. Hence, A. Himanshu Kumar 1 answered Oct 1, 2017 Himanshu Kumar 1 comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes answer c is correct because the hardware support for virtual memory mapping to physical memory are registers required for page table implementation basically PBTR register and TLB for caching the pages, now because the concept of virtual memory is removed hence no hardware components are required. ankur_mahiwal answered Jan 19, 2015 ankur_mahiwal comment Share Follow See all 2 Comments See all 2 2 Comments reply Piyush commented Jan 19, 2015 reply Follow Share without virtual addressing we can do sharing of memory??? 1 votes 1 votes Ram Swaroop commented Mar 8, 2020 reply Follow Share But hardware support also required in contiguous memory allocation as well as paging not only virtual memory right So A is best answer 0 votes 0 votes Please log in or register to add a comment.