Caches

• Once you have completed the VA to PA translation you have the physical address. What's next?
• You need to access memory with that PA
• Instruction and data caches hold most recently used (temporally close) and nearby (spatially close) data
• Use the PA to access the cache first
• Caches are organized as arrays of cache lines
• Each cache line holds several contiguous bytes (32, 64 or 128 bytes)

Addressing a Cache

• The PA is divided into several parts

• The block offset determines the starting byte address within a cache line
• The index tells you which cache line to access
• In that cache line you compare the tag to determine hit/miss