Memory timing

Keep recently accessed data in higher levels of memory hierarchy (i.e. use better memory).

Hit or miss

Hit is when data is found in that level of memory hierarchy. Miss is the complement.

Average memory access time

$AMAT=t_{cache}+MR_{cache}[t_{MM}+MR_{MM}(t_{VM})]$

Note that if memory is not in main, it must be in virtual