Consider an Architecture That Uses Virtual Memory, a Two-Level Page

Essay

Consider an architecture that uses virtual memory, a two-level page table for address translation, as well as a TLB to speed up address translations. Further assume that this machine uses caches to speed up memory accesses. Recall that all addresses used by a program are virtual addresses. Further recall that main memory in the microarchitecture is indexed using physical addresses. The virtual memory subsystem and cache memories could interact in several ways. In particular, the cache memories could be accessed using virtual addresses. We will refer to this scheme as a virtually indexed, virtually tagged cache. The cache could be indexed using virtual addresses, but the tag compare could happen with physical addresses (virtually indexed, physically tagged). Finally, the cache could be accessed using only the physical address. Describe the virtues and drawbacks for each of these systems. Be sure to consider the case where two virtual addresses map to the same physical address.