Computer Architecture: Elements of Cache Design Quiz

Cache Design Elements

• Cache design aims to improve memory access speed by storing frequently accessed data closer to the processor.
• Effective cache design involves balancing cache size and access time.

Cache Size

• Cache size is a critical factor, as larger caches can store more data but may have longer access times.
• A balance between size and speed is essential.

Cache Lines

• Cache memory is divided into lines or blocks, each storing a fixed amount of data.
• When the processor requests data, an entire line is loaded into the cache, increasing the likelihood of future data requests being satisfied from the cache.

Associativity

• Associativity refers to how the cache is organized in terms of mapping data from main memory.
• There are three types of associativity:
  • Direct-Mapped Cache: Each block of main memory maps to exactly one cache line.
  • Set-Associative Cache: Each block of main memory can map to a set of cache lines.
  • Fully Associative Cache: Each block of main memory can map to any cache line.

Replacement Policy

• When a cache is full, a replacement policy determines which existing item should be evicted to make room for the new one.
• Common replacement policies include Least Recently Used (LRU), First-In-First-Out (FIFO), and random replacement.

Write Policy

• Write policy determines how writes to the cache are handled.
• There are two types of write policies:
  • Write-Through: Data is written to both the cache and main memory simultaneously.
  • Write-Back: Data is written to the cache first, and then to main memory at a later time.

Block Size

• Block size is the size of the data block transferred between main memory and cache.
• A larger block size can reduce the number of memory accesses but may result in more data being loaded into the cache.

Cache Hierarchy

• Modern systems often have multiple levels of cache (L1, L2, and sometimes L3).
• Each level has different characteristics in terms of size, speed, and proximity to the CPU.
• Efficient coordination between these levels is vital for overall system performance.

Write Buffer and Prefetching

• A write buffer may be used to temporarily store write operations before they are written to the main memory.
• Prefetching involves predicting what data the processor will need next and loading it into the cache before it is actually requested.
• This can help reduce latency.