I’ve looked at a few different articles related to this already but none of them explain the solution in a way that I can understand and replicate. I need to know how to translate a physical address to a virtual address in memory based on the following:
A simple virtual memory system has 32KB physical memory with 16-bit virtual address, of which 12 bits are used as offset. The following is the current content of the page table of one of the processes:
So basically I think the page size of this virtual memory system is 1024KB. I need a process to find the corresponding PA of VA B2A0. If you can give me the process I can go from there, you don’t have to give me the final solution 🙂
Thanks in advance guys. Also, if you know of an article that does this already and I’ve just missed it, feel free to just link me to that.
Cheers.
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Answer
32 KB is 2^15. so there are 15 bits for every physical address, lower 12 of them are used as offset, higher 3 as a number of pageframe.
What virtual page does 0xb2a0 resides in? To determine this, we need to take bits of the address, higher than 2^12. The size of a page is 2^12, that is 4096 or 0x1000, so it is a virtual page number 0xb = 11 (floor of 0xb2a0 / 0x1000). Offset inside the page is 0xb2a0 modulo 0x1000, it’s 0x2a0.
Then use the table to translate the virtual page number 11 to a physical pageframe. The virtual page is present (1), and it corresponds to the physical frame number with higher bits 111, that is 111 + twelve 0 in binary, => 0x7000 – it is the address of the start of the physical frame.
Our physical address resides at offset 0x2a0, so, the sought physical address is 0x7000 + 0x2a0 = 0x72a0.
Please, follow this flow and make it clear for you. If you have questions, read the Wikipedia first and if something is still not clear, ask 🙂