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How do I find what the memory system latency (access time) is for a memory system?

  1. Jun 17, 2012 #1
    I've been searching for some type of equation or explanation of how to find the latency (access time) of a memory system when given the bandwidth, the precharge (refreshing) time between accesses, and how many bytes of data are being transferred...

    Also I am not sure as to how memory interleaving would change this latency...

    Any help is greatly appreciated!
     
  2. jcsd
  3. Jun 17, 2012 #2

    phyzguy

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    Re: How do I find what the memory system latency (access time) is for a memory system

    It depends on the architecture of the memory, so I don't think there is a general relation. A serially architected memory can have a very long latency, but then a very high bandwidth once you've arrived at the correct location, while a random access memory will have a much smaller latency.
     
  4. Jun 17, 2012 #3
    Re: How do I find what the memory system latency (access time) is for a memory system

    Thanks for that information, but maybe it'd help if I just posted my homework question:

    Assume a memory system has a bandwidth of 120 MBytes (M = 2^20) per second and has aprecharge (refreshing) of 5 ns between accesses. What is the memory systems latency (access time) for the following two cases?

    a. Two bytes of data are transferred and memory interleaving is not used.

    b. 4-way memory interleaving is used and each module is able to transfer two bytes per access.

    I am unsure how to start this. I found a computer engineering equation that latency = seek time + rotational delay + transfer time + controller delay, but I have no idea how to apply this general form of a latency equation (or if I am supposed to use this equation at all) to this type of problem.

    Thank you very much!
     
  5. Jun 17, 2012 #4

    rcgldr

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    Re: How do I find what the memory system latency (access time) is for a memory system

    This is a formula used for hard drives, not system memory.
     
  6. Jun 17, 2012 #5
    Re: How do I find what the memory system latency (access time) is for a memory system

    OK.. is there a formula for the latency of system memory/what is it?
     
  7. Jun 17, 2012 #6

    rcgldr

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