How to read CPU-Z when system is OC

Discussion in 'CPUs and Overclocking' started by jrsc, Dec 31, 2003.

  1. jrsc

    jrsc Junior Member

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    I was going over some memory articles/reviews as I'm looking for an upgrade from my current system and I came across this screenshot of CPU-Z. The frequency of the memory says its running at 160.4MHz on a 512MB Dual Channel DDR PC3700 which is suppost to run at a speed of 466MHz.

    I would like to know how the tests are done in understanding memory speed. For example, how Anandtech tests the memory's in their articles? If CPU-Z says that the particular memory stick is running at 160.4MHz, what is it really running at?

    Is it safe to say that since its DDR (double data rate) the speed rating in CPU-Z is just the speed one way? So if I just double that 160.4MHz, the actual speed of the memory tested in that article is 320.8MHz? That still doesn't explain why the PC3700 DDR466 memory is running at 320.8MHz.

    Lastly, when a memory is rated DDR333 or DDR400. Does that really mean its running at 333MHz and 400MHz respectively? Or is that just a top rated speed that they can run at? Because if my example and thinking above is correct, then wouldn't it mean the memory isn't running at its optimal speeds?

    Please explain and correct me.
     
  2. Amused

    Amused Elite Member

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    CPU-z shows the actual frequency the RAM is running at. To know the FSB of the system, just multiply by the multiplier. (...x14, x15, x16 and so on)

    Do this math:

    My CPU-z screen reads on the front page:

    Core Speed: 3600.00
    Multiplier: x 16
    FSB: 225.0 (225 x 16 = 3600)
    Buss Speed: 900.0 (225 quad pumped = 900)

    This is with a 1:1 divider.

    The math changes with a 5:4 or 3:2 divider.

    333 and 400 are the rated speed at which the RAM is guaranteed to run.

    Some people run 5:4 or 3:2 dividers and keep their RAM underclocked to get their CPU to high speeds, so their RAM frequency will be lower than normal.

    A quick look at the Memory Tab in CPU-z will tell you what divider is being run.

    What I see on my memory tab:

    Frequency: 225.0 MHz
    FSB: DRAM: 1:1 (this is the ratio or "divider")
    CAS # Latency: 2.0
    Cas# to RAS# Delay: 3
    RAS# Precharge: 2
    Cucle Time (Tras): 7
     
  3. bootoo

    bootoo Senior member

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    cpu-z fluctuates a lot when you overclock. I don't know why.

    I've heard that cpu-id (older rev, not the newest) is better but couldn't tell you.

    I use aida 32 when I can't get a clear cpu-z reading, hope that helps
     
  4. Amused

    Amused Elite Member

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  5. jrsc

    jrsc Junior Member

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    So in your case, if you were to run CPU-Z in its current state of 1:1, it would show the memory speed to be 225MHz? I was questioning how the PC3700 DDR466 was only rated at 160.4MHz? But with your input, I now understand why it was running at 160.4MHz.

    Given a ratio of 5:4 (assuming the FSB is 200), I now see why its at 160.4MHz. My impression of OC was to get the most speeds out of your setup, memory included. Hence the faster the better. Is having too high of a memory speed not good?
     
  6. Amused

    Amused Elite Member

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    It can be if it causes instability. It also depends on what you do. Some programs need all the memory bandwidth they can take, others are CPU intensive without needing gobs of memory bandwidth. As a gamer, I need bandwidth... and lots of it.

    Anand's article is trying to show that faster DDR speeds ARE a good thing. The CPU-z screen shot you are seeing is a test of lower DDR speeds.
     
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