L2 Cache

Discussion in 'Buying Tips and Advice' started by DarkRevenant, Jun 12, 2008.

  1. DarkRevenant macrumors member

    Joined:
    Mar 22, 2008
    #1
    Can anyone explain L2 cache in relatively simple terms? The point being, how much of a difference does 3mb of L2Cache vs. 6mb of L2Cache make? (Low End MBP vs Mid Range MBP).

    Thanks.
     
  2. samh004 macrumors 68020

    samh004

    Joined:
    Mar 1, 2004
    Location:
    Australia
    #2
    The L2 cache is easier to go to than RAM, it's faster. There is a lengthy review here that discusses the differences between a 4MB, 2MB and 1MB cache. The conclusion sums it up well, that not all applications see a huge benefit (it varies), but the difference between 4MB and 1MB is a lot even in standard applications, so 3MB to 6MB might be noticeable too.
     
  3. B1gMac macrumors regular

    B1gMac

    Joined:
    Jun 2, 2008
    #3
    I have heard a lot of people choosing not to upgrade their memory cards (from 2 GB to 4 GB) through apple, but buying it separately and installing it themselves. I was wondering, can the same be done with L2 cache? How much would it cost, and how difficult would it be to upgrade from 3mb to 6mb on my brand new MBP?
     
  4. H$R macrumors 6502

    H$R

    Joined:
    Apr 1, 2008
    Location:
    Switzerland
    #4
    L2 cache is a feature of the processor. You can't upgrade the L2 cache alone, you have to upgrade the processor itself. So you would have to buy a whole new processor and fit it onto the motherboard. That doesn't make any sense for you're MPB, because you just could have chosen the faster chip (with 6 mb L2 cache) in the first place.

    With RAM it's something different, that's a part for itself, which is just overpriced if the upgrade is done by Apple.
     
  5. B1gMac macrumors regular

    B1gMac

    Joined:
    Jun 2, 2008
    #5
    Thank you for explaining that!

    Now, could you explain why the cache is so small? If it makes your computer SO much faster, why don't all computers have at least 6 mb? (I thought memory prices were quite low right now, so I'm assuming it doesn't cost much to have a greater L2 cache)... But correct me if I'm wrong.
     
  6. illidian macrumors 6502

    Joined:
    Mar 27, 2008
    Location:
    Cincinnati, OH
    #6
    Completely different technology. You're comparing apples to hamburgers.

    L2 cache is part of the processor.

    RAM is not a function of the processor and has its own slots on the motherboard.
     
  7. MattZani macrumors 68030

    MattZani

    Joined:
    Apr 20, 2008
    Location:
    UK
    #7
    Whilst memory prices are low, fitting say 1Gb onto a CPU would be 1. Impossible, and 2. If possible, really expensive.

    Also, eventually you wouldnt notice a difference, aslong as there was RAM, the L2 Cache just stores info, before it is passed into the RAM. Well, thats how i have understood it.
     
  8. ChrisA macrumors G4

    Joined:
    Jan 5, 2006
    Location:
    Redondo Beach, California
    #8
    Your wrong. ;-)

    The L2 cashe is on the same chip as the processor. with curent processor much of the space on the chip is taken up with cache. If Intel doubled the amount of L2 then they could get only half as many processors per waffer. Basically doubling the L2 would almost double the cost of the processor.

    The way cache works is to reduce to average time to access memory. With cache the average times is the (speed of cache) times (the porbibilty of the data being in cache) plus (the speed of RAM) times (one minus the porbibilty of the data being in cache)

    You can see that you don't gain much after the porbibilty of the data being in cache get up to about .9 Doubling the size might get you to .95 but is 0.05 worth $300 of added cost? The engineers and marketers at Intel work together to figure tis kind o of stuff out.
     

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