Real world difference between 3 and 6mb of cache?

Discussion in 'Buying Tips and Advice' started by moworks2, Feb 26, 2008.

  1. moworks2 macrumors member

    Joined:
    May 3, 2007
    #1
    "2.4GHz Intel Core 2 Duo processor with 3MB on-chip shared L2 cache running 1:1 with processor speed; or 2.5GHz or 2.6GHz Intel Core 2 Duo processor with 6MB L2 cache"

    Can someone explain what difference we'll see between 3mb and 6mb of L2 cache please...

    I mean in application, software, video, what will the MBP do better?...I'd just like to know if the differences between the 2.4 and the 2.5 MBP are worth $500...

    thanks...

    M
     
  2. DrGruv1 macrumors regular

    Joined:
    Jan 29, 2002
    Location:
    Chicago - West 'Burbs
  3. BlizzardBomb macrumors 68030

    BlizzardBomb

    Joined:
    Jun 15, 2005
    Location:
    England
    #3
    L2 cache is basically very quick memory that the processor can use to speed things up. In everyday use, the benefit (including the additional .1 GHz clock speed) will be about 5 - 10%. If 5% more performance (and 512 MB of VRAM which is pretty pointless on a relatively weak GFX card like the 8600M GT) is worth $500 to you, go for it, but the smart money is with the base model and the 17".
     
  4. Ombatay macrumors newbie

    Joined:
    Feb 26, 2008
    #4
    This was the best website I found which actually talks about the difference between the 3mb vs the 6 mb L2 cache. Also makes some really interesting comparisons between the 2.4 GHz merom vs the 2.4 GHz penryn. Scarily close in performance, meaning that if you buy the base model, you're really just buying a multi-touch trackpad, as the old midmodel is available refurb for 1650$ right now. For 1650 I'd feel like I can actually justify the MBP over the MB.

    Now if only I could shake the feeling that down the road I'll really be glad I have the 512 mb vram and 6 mb L2 cache. Might save me some serious quid... But my girl has the Air, and although it's entirely frivolous at this point as I don't do any serious photo-editing, the multi-touch trackpad is so gd nifty, and I think I like it just enough to justify it, esp seeing those patents and what may be with a software update.
     
  5. Baumer582 macrumors member

    Joined:
    Feb 20, 2008
    #5
    So Apple is making the base and mid-levels only different by 5% for an extra $500??

    Will the difference really be that small? What about when running programs like Final Cut or Photoshop?
     
  6. Am3822 macrumors 6502

    Am3822

    Joined:
    Aug 16, 2006
    Location:
    Groningen, The Netherlands
    #6
    I think that it's also interesting to see what's the difference between the old models (4MB cache) and the new ones.
     
  7. deboni macrumors member

    deboni

    Joined:
    Jun 9, 2007
    Location:
    Oakland, CA
    #7
    lecture on cache memory

    The whole idea of cache memory is to increase expense slightly but decrease average memory access time significantly. Say it takes 10 clocks cycles for the cpu to access something in RAM, 6 cycles to access Level 2 cache, 3 cycles to access Level 1 cache, and one cycle to access internal registers. Now, if you can say what percentage of memory accesses will be satisfied by each of these levels of storage, you can calculate an average access time. Of course, RAM must be loaded from disk, but once the program is launched, this has probably been done, unless you're using virtual memory, in which case the average access time will be increased by percentage of accesses that must be loaded from disk. Cache, too, must be loaded, and since it's smaller than RAM (L1 will be smaller than L2, as well), its contents will likely change frequently in the course of program execution.

    Complicated strategies have been invented to manage the use of cache, but by and large, one can say that it all works on the principle(s) of locality. When a memory access cannot be satisfied by cache, it comes from RAM, but some number of other nearby items will be fetched from RAM into cache along with the needed one, on the assumption that they'll be needed soon. So cache miss costs can be amortized over several accesses that will "hit" because their targets were loaded along with the "missed" item.

    Generally, there are only broad ways to answer a question like, "how much will this much cache gain me over a smaller amount on a faster processor?" It depends on the applications you run. Some apps - say, graphics or games - are engineered to run more efficient special purpose instructions than, say, a word processor might. This can gain you significantly over and above concerns about cache size.

    The best way to answer such questions is to measure performance of the desired apps on particular machines. That said, more and faster is usually better.

    Tom
     
  8. moworks2 thread starter macrumors member

    Joined:
    May 3, 2007
    #8
    yeah, i'm thinkin' the base model would do me fine...thanks BB...
     
  9. moworks2 thread starter macrumors member

    Joined:
    May 3, 2007
    #9
    I'd like to know about that as well...my main applications are Photoshop, Lightroom, Illustrator, and Indesign...no games, not much video...although I will burn a dvd, make a copy of the films i buy, once in a while...
     
  10. kssgill macrumors newbie

    Joined:
    Feb 27, 2008
    #10
    Blue Ray

    Assuming that their will be a future option for BlueRay dvd via USB 2. Looking at dell site the minimum requirement for Blue ray on dell site for an equivalent model is "A processor Model 7100 or Higher and Nividia GEFORCE GO8600M GT" video card.

    Aka MacBook will not have the minimum required graphs video card to support Blue Ray.
     

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