Title: 544
Tags: lec8

Q: Before a CPU can add two values in RAM, what must it do?
A: Load those values to CPU registers

Q: Which CPU cache is fastest?
A: L1

Q: Which CPU cache is biggest?
A: L3

Q: When data in a cache is too old and no longer valid, we say it is _______
A: stale

Q: What does FIFO stand for?
A: First In First Out

Q: What does LRU stand for?
A: Least Recently Used

Q: How are FIFO and LRU similar?  How are they different?
A: They are the same for a miss: the data is added to the cash, in the "newest" position.
They are different for a hit: FIFO does not change how it prioritizes the item, but LRU resets it to the "newest" position.

Q: What do you call it when you find an item in a cache?
A: "hit"

Q: What do you call it when you CANNOT find an item in a cache?
A: "miss"

Q: What is a pattern where a random eviction policy would beat LRU and FIFO?
A: A common pattern is that the data is too big to fit completely in cache, and the program loops, repeatedly reading over the dataset in the same order.  LRU and FIFO will have a 0% hit rate, but random will at least get some hits.