Editing CPU cache (section)

====CPU stalls====
The time taken to fetch one cache line from memory (read [[Latency (engineering)|latency]] due to a cache miss) matters because the CPU will run out of work while waiting for the cache line. When a CPU reaches this state, it is called a stall. As CPUs become faster compared to main memory, stalls due to cache misses displace more potential computation; modern CPUs can execute hundreds of instructions in the time taken to fetch a single cache line from main memory.

Various techniques have been employed to keep the CPU busy during this time, including [[out-of-order execution]] in which the CPU attempts to execute independent instructions after the instruction that is waiting for the cache miss data. Another technology, used by many processors, is [[simultaneous multithreading]] (SMT), which allows an alternate thread to use the CPU core while the first thread waits for required CPU resources to become available.