Section 12.7
Review Questions

Hardware

  1. Why do computer designers use extra hardware to implement virtual memory?
answer...
to speed up its average performance
  1. What is the extra chip that some computers used to have to do memory address translation?
answer...
MMU (memory management unit)
  1. What happened to this chip? Is it no longer needed?
answer...
it is now commonly bundled up with the ALU and registers on the main chip; its functions are still needed
  1. What French word does the term cache derive from and what does it mean?
answer...
cacher -- to hide
  1. What is a cache?
answer...
a small secret chunk of very high speed memory that sits between the processor and main memory and holds the more recently accessed data
  1. Where can a system keep the page table?
answer...
in registers, in main memory, or in the cache
  1. What are some of the trade-offs and issues involved with the decision where to keep the page table?
answer...
in registers    -- the page table will be very limited in
                   size, though very fast
in memory       -- the page table can be as large as you want,
                   but accessing it will be very slow
in cache memory -- the page table is somewhat limited in size,
                   though it will be very fast
  1. Realize that each process (program in execution) requires its own separate page table! What does this imply in terms of memory usage?
answer...
that there is a significant memory overhead in using virtual memory in a multiprogrammed system. You'll need lots more real memory!