1) You are using a 1 GHz system with paged virtual memory for doing a real-time application. No other application is running on the system. A real time application is one where each task must be finished within a guaranteed time bound. In this particular real-time application, there are many tasks; each runs the exact same code but with different data each time. Each real-time task reads 20 bytes from an I/O device, performs some processing on it, and writes the updated 20 bytes of data back to the I/O device. I/O reads or writes are performed at 20 MB/sec. The code to process the 20 bytes has a total of 10 loads and stores, and takes 10000 cycles when all memory accesses are cache hits. These loads and stores can access anywhere in virtual memory. The system transfers control to another task with an overhead of 1000 cycles.
Every memory access takes 25 ns and every disk page transfer from the virtual memory swap space takes up to 2 ms. In the worst case a load or store could require 4 memory accesses and 2 disk transfers. How many real-time tasks can be guaranteed to run on this system per second in the worst case? (Assume the worst-case virtual memory behavior)
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2) A page table is indexed by the virtual page number to obtain the physical address of the block. Given a 28-bit virtual address, 4 KB page size, and 4 bytes per page entry, what is the maximum size of the page table assuming byte-addressable memory?