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What is L2 cache?

Discussion in 'Macintosh Computers' started by powder8, Apr 20, 2004.

  1. macrumors newbie

    What does L2 cache do? Would there be any noticable difference from the previous generation 1ghz iBook with a 256k L2 cache to the new generation 1ghz iBook with 512k L2 cache.... If there is, what type of applications would benifit the most from this increased L2 cache?

  2. macrumors 6502a


    A cache is a place that the CPU can keep data that is most recently accessed for much faster access than retrieving it from main memory again. For example, if you had some text like "Macintosh" that you used a lot in a program, then it could be placed into the cache where it can be access more quickly than from main memory.

    Now, since there are often multiple caches in a computer system, they are given levels. The lower the level, the faster and usually the smaller the cache is. All PowerPC processors come with an L1 cache that is incredibly fast (accessing data in the L1 cache is as fast as executing many simple instructions). Most machines also have an L2 cache, which while usually not quite as fast as the L1 cache is also quite a bit larger, allowing you to store more data near the CPU. You can have as many levels of cache as you want, but usually you only see 2 or 3 levels.

    Thus larger caches allow more data to be stored for fast access, and since the CPU manages what is in the cache, all applications benefit from faster/larger/more caches automatically.
  3. macrumors regular

  4. macrumors 68030


    Basically L2 cache is Level 2 Memory that is placed on the Processor chip now days. To play most games or use high-end software you need as much cache as you can get on the processor also a lot of RAM. Most tech experts will recommend Pentium 4's because they have 32KB L1 cache (AMD Duron has 64KB) 20 static and like 12 opt cache. The L2 is from 256 up to 1MB depending on the Pentium 4, Celerons have 128 up to 256 on L2 (thats why they are so cheap), Pentium 4 is now starting to embed (with the extreme edition) L3 cache with up to 2MB. A simple example would be like this: You need to get important instructions for a project to your friend. Your friend lives 5 blocks away. If you were to walk there that would be like RAM, RAM has to move into the CPU when the CPU is able to take in more instructions so when your friend is finished with those instructions you have to keep walking there to give him more depending on how many instructions you have. Well to speed things up (L2 or L3 cache) you could call him and give him the instructions or be standing there telling him what to do.

    FRIEND(CPU) _ _ _ _ _ YOU 5 blocks away (RAM)

    FRIEND(CPU) YOU(L2 cache) on phone or just cm away from him

    L2 cache
    L3 cache

    I'm sorry if I confused you, but thats an example way of explaining it
  5. macrumors regular


    Very nice explanation. Well done. :)

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