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Thread: cache??




  1. #1
    Join Date
    May 2002
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    What exactly does the cache do on a processor, and what would be the lowest recommended??? Thanks!!!

  2. #2
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    Dec 2001
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    The CPU is crunching on something, and the different levels of cache are storage places for little bits of data ready for the CPU to work on. More is usually better. The reason I say usually is because the Prescott core Pentium 4's with the 1MB of L2 cache do not perform any better than the equivalent, and older, Northwood core P4's at the same clock speeds.

    The cache on the CPU core is made of high speed SRAM that runs the same speed as the CPU. SRAM does not need to be refreshed like DRAM (SDRAM, DDR SDRAM, RDRAM), and is extremely expensive, so having tons of it generally isn't feesible for pretty much everyone.

    Since it's on the CPU, you're no longer able to buy more SRAM and drop it in.
    Back in the Socket 7 days, there was something called Cache on a Stick (COAST), but that's been gotten away from for several years.

    This is the primary reason why Durons and Celerons are cheaper than Athlons and Pentium 4's.

  3. #3
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    Nov 2003
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    It's also the primary reason Athlon XPs and Pentium 4s are better than Celerons and Durons of much higher frequency. A Celeron 2.4 GHz can't stand up to an Athlon XP of less than 2GHz because it will have much less cache.

    Think of cache as a layer of memory between you and your processor (which it is).

    First there's your paging file, which is on your hard drive. This is the slowest.
    Then there's SDRAM, DDR SDRAM, or RDRAM. This is much faster than HDDs. It's also much more expensive.
    Next is your cache. There are generally two or three levels, and usually the higher the level, the more cache. These are much faster than regular Random Access Memory. Again, more expensive.
    Finally there is the proccessor's own memory. Most commonly 16 bits, 32 bits, or 64 bits. It's much, much faster than the other kinds. Yet again, much, much more expensive. Plus, there are obstacles to jump through when a manufacturer adds more of this memory to a CPU. It takes years of devolopment to invent a processor with more memory than the standards.

    These layers are necessary to get instructions from your software to your CPU in a timely manner. Without at least one level of cache, RAM, and CPU core memory, you computer would not function.

    In any case, you needn't mess with the cache on the processor. It's not something you really get to mess around with like an HDD or RAM.

  4. #4
    Join Date
    May 2002
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    Thanks for your help! I understand it much better now. I am looking at getting a new PC, and while I have a decent understanding of how things work, I didn't fully understand why there were differences in the cache on the processesors.

    Again, I appreciate all the help this forum has brought me.

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