Cache memory is a very high speed memory built in the processor and it is used between main memory (RAM) and the processor.
A CPU cache is a cache memory used by the CPU of a computer to reduce the average time to access the main memory. The Cache is a smaller, faster memory as the memory which stores copies of the data from the most frequently used main memory location.
The high-speed memory used for the Cache purpose is very costly that is the reason it is not used as the main memory of the computer. The information frequently required by the processor is kept in the cache memory by the Cache controller.
This Cache controller always tries to make sure that the data required by the processor in the next memory access is available in the Cache memory. This improves the speed of the computer very much because the required data is in the cache memory it is made available to the CPU without any wait state.
In case of a cache hit the processor immediately reads or writes the data in the data cache line. The proportion of accesses that result in a cache hit is known as the hit rate and is a measure of the effectiveness of the cache.
When the required data is not available in the cache memory it is called a miss. In case of a cache miss, most caches allocate new entry, which comprises the tag just missed and a copy of the data from memory. The reference can then be applied to the new entry just as in case of a hit.
Misses are comparatively slow because they require the data to be transferred from the main memory. This transfer incurs a delay since main memory is much slower than cache memory.
The performance of the cache depends on the following:
- Speed and size of the Cache memory
- The logic used to read data around the memory area read by the CPU.
- The logic used to guess the next required data by the processor.
Most of the new micro processors have the Cache memory added in the CPU chip itself to speed up the process even further. Even on these CPUs with built-in internal Cache, you can add external Cache.
Que- which type of memory is primarily used as cache memory? Ans- RAM (Random Access Memory.
Que - some of the cache memory of a CPU is ? Ans- Some of the cache memory of a CPU is inside the CPU, itself
Query- cache memory is a form of rom.