A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost (time or energy) to access data from the main memory. A cache is a smaller, faster memory, located … See more

Early examples of CPU caches include the Atlas 2 and the IBM System/360 Model 85 in the 1960s. The first CPUs that used a cache had only one level of cache; unlike later level 1 cache, it was not split into L1d (for data) and L1i (for instructions). Split L1 cache started in … See more

Cache row entries usually have the following structure:
The data block (cache line) contains the actual data fetched from the main memory. The tag contains … See more

Most general purpose CPUs implement some form of virtual memory. To summarize, either each program running on the machine sees its own simplified address space, which contains code and data for that program only, or all programs run in a common … See more

When trying to read from or write to a location in the main memory, the processor checks whether the data from that location is already in the cache. If so, the processor will … See more

The placement policy decides where in the cache a copy of a particular entry of main memory will go. If the placement policy is free to choose any entry in the cache to hold the … See more

A cache miss is a failed attempt to read or write a piece of data in the cache, which results in a main memory access with much longer latency. There are three kinds of cache misses: instruction read miss, data read miss, and data write miss.
Cache read misses … See more