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Thread: RAM Speed VS Latency

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    ROG Renaissance Man Array Florre's Avatar
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    RAM Speed VS Latency

    What is more important ram speed or latency?

    2400mhz with latency 10-11 or 1866mhz with latency 9?
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    For what ?
    Gaming with a PCI-Express VGA ? None.
    Desktop usage ? None.
    A few applications ( WinRAR, 7-zip, WinZIP, KGB, SAP, high traffic SQL Server ) ? The best of both worlds, and also depends on the platform ( chipset + CPU )

    If you're talking about your system, and your primary usage ( which is gaming most likely with your GTX 580 SLI ) then... get a decent DDR3-1600 memory kit with the capacity of your desire ( anything from 6GB and more is the top you can get for gaming performance ).

    Data and proof to back it up ? Sure, go ahead and read my extended testing article

    http://www.benchzone.com/page.php?al...formance_part1

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    ROG Guru: Diamond Belt Array Zka17's Avatar
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    Regarding the system memory the most important is to have it running stable... a bad memory can really mess up things... - whatever settings you choose, run memtest86+ for at least 4 cycles, if it passes, then most likely you're fine...

    If you're in benching, then 2400MHz CL10 is better than 1866MHz CL9... - just be aware that not all systems are the same, and there is no guarantee that you can actually reach those memory speeds... (it's about the chip's lottery)

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    et tu ROG Array Arne Saknussemm's Avatar
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    There is a formula that can help you in deciding if one kit is faster than the other when the timings are taken into account.

    (CAS/frequency) x 2000 gives you a number in nanoseconds for comparing speeds.

    Say you see a 1600 kit at 7-8-7-20 and a 1866 kit at 9-10-9-28 which is faster?
    Well 7/1600 x 2000 = 8.75 nanoseconds; 9/1866 x 2000 = 9.646 so the 1600 kit actually looks quicker.

    If these numbers are close or the same choose the higher frequency it will be more efficient.


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    ROG Guru: Diamond Belt Array Zka17's Avatar
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    Arne, what you calculated there isn't the memory latency? If so, higher latency doesn't mean that your RAM is actually slower?

    So, 9.646 ns is actually worse than 8.75 ns... the first takes more time...

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    et tu ROG Array Arne Saknussemm's Avatar
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    Correct! the latency is the CAS no..... the formula uses latency not calculates it......it lets you know which kit is faster when comparing different speed RAM with different latencies.... I thought Florre might have been wanting to know that (maybe my mistake).

    1866 cas 9.. 9.6462 slow
    2400 cas 11.. 9.1666 faster
    2400 cas 10.. 8.3332 fastest
    Last edited by Arne Saknussemm; 03-29-2013 at 06:57 PM.


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    ROG Renaissance Man Array Florre's Avatar
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    Quote Originally Posted by Arne Saknussemm View Post
    Correct! the latency is the CAS no..... the formula uses latency not calculates it......it lets you know which kit is faster when comparing different speed RAM with different latencies.... I thought Florre might have been wanting to know that (maybe my mistake).

    1866 cas 9.. 9.6462 slow
    2400 cas 11.. 9.1666 faster
    2400 cas 10.. 8.3332 fastest


    Thanks for the formula. Its proving to be damn useful!

    Thx.
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    et tu ROG Array Arne Saknussemm's Avatar
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    Good stuff!


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    ‎‎‎‎‎‎‎‎‎‎ Array Gorman's Avatar
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    Quote Originally Posted by Arne Saknussemm View Post
    (CAS/frequency) x 2000 gives you a number in nanoseconds for comparing speeds.
    Could you explain this formula?

    Looking at the units I see CAS is in clock cycles, frequency is mega clock cycles per second, so the formula yields an answer in micro seconds.
    So where does the 2 come from? I'm guessing this is an approximate formula, and the real one uses a second point of data; (CAS+???)/F * 1000 ?

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    et tu ROG Array Arne Saknussemm's Avatar
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    Not thought about it much... might hide a multitude of simplification but works as a comparative for kits I believe.

    Hmm but If CAS is measured in nano seconds divide by x thousand times y thousand still nanoseconds no?

    http://rog.asus.com/forum/showthread...l=1#post195744


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