What is the purpose of L1, L2 and L3 cache in processor

[senthil_kumar_1]

Hi All,

I would like to know what is the purpose of L1, L2 and L3 cache in processor in detail.

[cnb · Accepted solution]

In detail:

http://en.wikipedia.org/wiki/CPU_cache#Cache_hierarchy_in_a_modern_processor

Rgds,

[senthil_kumar_1]

If we there are dual core in one processor, then the same L1, L2 and L3 caches will be shared by those two core?

[Torsten.]

It depends, but most of the times higher levels are shared between cores.

[cnb]

> It depends, but most of the times higher levels are shared between cores.

Exactly. You would need to look at the CPU Manufacturer specifications for each processor designed.

Rgds,

[Kranti Mahmud]

Hi Senthil,

CPU cache memory is a high speed memory kept in between processor and RAM to increase the data execution speed. It is kept near to the processor.There are different levels of cache.

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.

L2 cache comes between L1 and RAM(processor-L1-L2-RAM) and is bigger than the primary cache (typically 64KB to 4MB).

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.

http://en.wikipedia.org/wiki/CPU_cache

Rgds-Kranti