Cache

Question 1

Temporal locality

Answer 1

data accessed will likely be accessed again soon, so save the data in a small storage that is fast. AKA cache

Question 2

Spatial locality

Answer 2

more likely to access data close to each other, so we fetch memory in blocks not just one entry at a time.

Question 3

Locality

Answer 3

programs tend to accessed data and instructions with address near or the same as data recently used.

Question 4

Describe a cache organization

Answer 4

sets, blocks, valid bit, tag, data itself

Question 5

Fully associated cache

Answer 5

each set only has one block

Question 6

2-way associated cache / n-way association

Answer 6

each set has two blocks or n blocks

Question 7

How to map address in a branch instruction to memory location

Answer 7

the address bits is split into offset, index, tag bits.
Index bits specifies which ‘set’, tag bits specify is data matches, offset is to access the right bit in a block.

Question 8

Cache miss

Answer 8

when the tag bits doesn’t match the tag in a set

Question 9

How does the offset, index and tag bits of an address change for n-way associative cache

Answer 9

n-way associative means. n blocks per set. so number of sets can be reduced by n times. so index bits can be reduced. giving more bits for tag matching. since there’s n times more tags now