Question

Main memory has 1,024 bytes, and frames are 32 bits. Assume a portion of main memory, and the page table, shown below. The frame numbers in the Page Table are shown as base 10, but all other data in the tables is either binary or hex. A TLB is not used. The virtual address space for each process is 8 pages. The first frame in memory is frame 0, but only a portion of memory is shown (not necessarily that part of memory that is frame 0).

Memory V 1 0 1 1 Page Table frame 169 280 169 165 78 170 242 128 address data 1010100100 Ox66 1010100101 Oxfa 1010100110 Ox62 1010100111 Oxa 9 1010101000 0x8c 1010101001 Ox2b 1010101010 Ox43 1010101011 Ox70 0 1 0 1

a) If the CPU receives the data 0x2b, then what is the virtual address request that was made by the CPU? PLEASE EXPLAIN.

b) If the CPU requests address 01010, what data is returned to the CPU?

Answer 1

Can you be more specific about the page table size.

a) from the Main memory table, we can see the address of the frame here 0x2b is present. i.e 1010101001

1010101001 = 681 in base 10

So, for the CPU to get data from this address, it first goes to the page table. The CPU finds the address of the page that contains 681 in the frame column of the page table. Since 681 isn't a part of the page table picture that you have given, we can't decide on the virtual address generated by the CPU. However if you could specify the page table size, we can conclude on the number of bits of the address of a page in the page table.

b) Since the CPU requests address 01010 ==> the CPU goes to page number with this address, i.e 10th page in the page table and there

if V column of the 10th page is 1( it indicates the page is in the main memory)

if V column of the 10th page is 0 ( it indicates a page miss, so the page has to be fetched from the disk)

then the CPU goes to the frame address mentioned in the frame column of the page table and fetches the data.