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Cache

Cache. Heng Sovannarith heng_sovannarith@yahoo.com. Definition. A memory cache, sometimes called a cache store or RAM cache, is a portion of memory made of high-speed static RAM (SRAM) instead of the slower and cheaper dynamic RAM (DRAM) used for main memory .

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Cache

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  1. Cache HengSovannarith heng_sovannarith@yahoo.com

  2. Definition • A memory cache, sometimes called a cache store or RAM cache, is a portion of memory made of high-speed static RAM (SRAM) instead of the slower and cheaper dynamic RAM (DRAM) used for main memory. • Memory caching is effective because most programs access the same data or instructions over and over. • By keeping as much of this information as possible in SRAM, the computer avoids accessing the slower DRAM.

  3. Level of Cache • Some memory caches are built into the architecture of microprocessors. The Intel 80486 microprocessor, for example, contains an 8K memory cache, and the Pentium has a 16K cache. • There are different levels of cache. • Level 1 • Level 2 • Level 3

  4. Cache Level 1 • L1-cache is the fastest cache and it usually comes within the processor chip itself.  • The L1 cache typically ranges in size from 8KB to 64KB and uses the high-speed SRAM (static RAM) instead of the slower and cheaper DRAM (dynamic RAM) used for main memory. • The Intel Celeron processor uses two separate 16KB L1 caches, one for the instructions and one for the data.

  5. Cache Level 2 • L2 cache comes between L1 and RAM (processor-L1-L2-RAM) and is bigger than the primary cache (typically 64KB to 4MB).  • Like L1 caches, L2 caches are composed of SRAM but they are much larger.

  6. Cache Level 2 (cont.)

  7. Cache Level 3 • L3 cache is not found nowadays as its function is replaced by L2 cache. • L3 caches are found on the motherboard rather than the processor. It is kept between RAM and L2 cache. • So if your system has L1,L2 and L3 cache data fetching will be L1->L2->L3->RAMie. If data is not there in L1 it will check L2 then L3 then RAM...

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