Cache

• What is the definition of cache?

  Cache is a fast-access storage area.
• What are the features of cache memory compared to main memory?

  • Speed: Cache is very fast; main memory is slower.
  • Size: Cache is small; main memory is large.
  • Cost: Cache is expensive; main memory is less expensive.
  • Usage: Cache stores frequently used data; main memory stores all data and programs.
• What happens when the CPU checks the cache for data?

  If data is found, it retrieves it quickly.
• What are the two main types of cache?

  Data Cache and Instruction Cache
• How does cache memory speed compare to main memory?

  Cache memory is very fast.
• What type of data does cache memory store?

  Cache memory stores frequently used data.
• What is the purpose of an Instruction Cache?

  • Stores instructions needed for program execution
  • Speeds up the running of programs
• Which cache would be more beneficial for speeding up program execution?

  Instruction Cache
• What occurs if the data is not in the cache?

  The CPU fetches it from main memory.
• Why does the CPU use cache instead of main memory?

  Cache is faster than main memory.
• If a CPU needs to access frequently used data quickly, which cache would it utilize?

  Data Cache
• If you wanted to access data that is not currently in the CPU cache, which component in the hierarchy would you access next?

  You would access the main memory next, as it is the next level in the hierarchy after the CPU caches.
• How does the size of each component in the CPU memory hierarchy differ?

  • CPU registers have the smallest size
  • Cache levels (L1, L2, L3) have progressively larger size
  • Main memory has a much larger size than the caches
  • Storage devices (Flash/SSD, Hard disk) have the largest size
• What is the fastest component in the CPU memory hierarchy?

  CPU registers
• Why are there multiple levels of cache (L1, L2, L3) in the CPU memory hierarchy?

  The multiple cache levels provide a trade-off between speed and size, with smaller but faster caches closer to the CPU
• What do cache levels create in computer architecture?

  A memory hierarchy
• Which is more expensive, cache memory or main memory?

  Cache memory is more expensive.
• How does the access time differ between the components in the CPU memory hierarchy?

  Access time increases from CPU registers to caches to main memory to storage devices
• How does a Data Cache function in relation to the CPU?

  It provides quick access to frequently processed data
• If a program needs to access data that is not currently in the CPU caches, which component in the hierarchy will it access next?

  Main memory
• What is the size comparison between cache memory and main memory?

  Cache memory is small.
• What is the difference in storage between Data Cache and Instruction Cache?

  Data Cache stores data; Instruction Cache stores instructions
• What type of data does main memory store?

  Main memory stores all data and programs.
• What is the cost relationship between L1 and L3 cache?

  L1 cache is more expensive than L3 cache
• Which cache level is the fastest?

  L1 cache
• What is the size of L1 cache compared to L2 and L3?

  Smallest
• How does the speed and access time of the components in the CPU memory hierarchy differ?

  • CPU registers have the fastest speed and lowest access time
  • Cache levels (L1, L2, L3) have progressively slower speed and higher access time
  • Main memory is slower than cache but faster than storage (Flash/SSD, Hard disk)
  • Storage devices (Flash/SSD, Hard disk) have the slowest speed and highest access time
• What are the components of the CPU memory hierarchy shown in the image?

  • CPU registers
  • L1 cache
  • L2 cache
  • L3 cache
  • Main memory
  • Flash/SSD
  • Hard disk
• Which cache level is the largest?

  L3 cache
• How does L1 cache compare to L3 cache in terms of speed?

  L1 cache is faster than L3 cache
• What is the speed of L2 cache compared to L1 and L3?

  Medium
• What is the cost of L3 cache compared to L1 and L2?

  Least Expensive
• Why is an Instruction Cache compared to having a recipe handy?

  It allows quick access to necessary instructions
• What is the largest component in the CPU memory hierarchy?

  Hard disk
• What does the CPU do first when it needs data?

  It asks for data
• What is a cache miss?

  Data not in cache, fetched from main memory
• What is a cache hit?

  Data found in cache, quickly retrieved
• What is the primary function of cache?

  To speed up data access
• How does the CPU use data from cache?

  It uses data directly from cache
• What happens during the cache check?

  The CPU checks if data is in cache