cache : Computer Hardware Buyers’ Glossary

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cache
Cache four meanings. It comes from the French cacher to hide. You need cache because the CPU (Central Processing Unit) is about 200 times faster than your main RAM (Random Access Memory) memory. The bottleneck in CPU speed is when the CPU has to go main memory for information, because it does not have a copy in cache. This overshadows everything else.
  1. L1 on-chip cache: Primary cache. Some extremely high speed RAM built right into the CPU chip to keep copies of the most frequently used items in regular RAM. It might be in the order of 512K to 1 GB.
  2. L2 static RAM cache: Secondary cache. Some high speed static RAM on the motherboard to keep the most frequently used items, in chips separate from the CPU. Now rare. In modern machines, the L2 cache may also be on the CPU chip.
  3. L3 static RAM cache: Tertiary cache. Some high speed static RAM on the motherboard to keep the most frequently used items, in chips separate from the CPU. This is usually large, expensive, and rare.
  4. disk cache: Some ordinary RAM used by the operating system to keep the most frequently used item on disk. This gives much faster access.
CPU caches
hard disk
RAM
ReadyBoost
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