03. Choose the correct alternatives (more than one may be correct) and write the corresponding letters only:
(iii) The total size of address space in a virtual memory system is limited by:
Answer is (a) and (b).
Virtual memory concept is independent of size of main memory and depends only on the availability of the secondary storage.
MAR holds the address generated by CPU and this obviously limits the total virtual memory address space.
MAR contain memory address. On systems with no virtual memory this is physical address. On VM systems, this address is virtual address. MAR hold the address generated by CPU and if this is holding physical address, then virtual memory cannot exist.
That part is not in that document. But CPU has no knowledge of actual address. And it is the CPU which writes to MAR. Hence, it should be virtual address. The below link makes this clear.
By "Virtual Memory system", they mean "process or program which we store in RAM" (Physical memory system means RAM itself)
A) is TRUE because if MAR size is 32 bits ..then we cannot have a process of size more than 232 addressable units (say Bytes)... If we have (232 +1) bytes then one of the byte cannot be accessed by CPU as MAR has only 32 bits instead of 33 bits ...
B) is TRUE because though we can have process of size more than the RAM size using Virtual Memory concept.. we cannot have a process of size more than Hard-disk size ...
C) is FALSE because we can have a process of size more than RAM as we saw ...
Good explanation. @Vicky rix