What happen on 32 bit machine with 256 MB Ram and 4KB page
Virtual to Physical address translation with Page Tables. Page offset examples. Virtual Page number and Physical Page number. Translation example.
On a 32-bit machine with 256 MB of RAM and a page size of 4 KB, several important things happen:
Address Space Limitations: A 32-bit machine can address a maximum of 2^32 (4,294,967,296) memory locations. With a 4 KB page size, the addressable memory space is divided into 4 KB chunks. So, the total addressable memory space would be 4 KB * 2^32, which is approximately 16 GB. However, in this case, you have only 256 MB of RAM, which is much smaller than the full addressable space.
Page Size: The page size is the minimum unit of data that can be transferred between main memory (RAM) and secondary storage (e.g., disk). In this case, the page size is 4 KB (4,096 bytes). It means that data is read from or written to RAM in chunks of 4 KB.
Virtual Memory: The combination of a 32-bit address space and 256 MB of RAM means that not all memory addresses can be mapped directly to physical RAM. Modern operating systems use a technique called “virtual memory” to overcome this limitation. Virtual memory allows the operating system to map a portion of the virtual address space to physical RAM and the rest to disk storage. When a process accesses a memory location that is not currently in RAM (a page fault), the operating system fetches the required page from disk into RAM, making space for it by swapping out another page if necessary.
Page Table: To manage virtual memory, the operating system maintains a data structure called a page table. This table keeps track of the mapping between virtual addresses and physical addresses. Each entry in the page table represents one page, and it contains the corresponding physical address if the page is present in RAM or information about where to find the page on disk if it is not in RAM.
Fragmentation: With a small amount of RAM (256 MB), there is a higher risk of memory fragmentation. Fragmentation occurs when the available memory is divided into small, non-contiguous blocks, making it challenging to find contiguous regions to allocate larger data structures, which can lead to inefficient memory usage.
Performance Impact: Due to limited physical RAM, frequent swapping of pages between RAM and disk may occur, resulting in increased disk I/O and reduced overall system performance. This situation is known as “thrashing,” where the system spends more time swapping pages than executing actual tasks.
In summary, on a 32-bit machine with 256 MB of RAM and a 4 KB page size, the limited addressable memory space and small amount of RAM could lead to challenges in memory management and performance issues. The operating system’s virtual memory system is crucial to make the most efficient use of available resources and to enable processes to run even when the required memory exceeds the physical RAM capacity.