1. Cache Heng Sovannarith 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->RAM ie. If data is not there in L1 it will check L2 then L3 then RAM...