RAM Timings - tRFC and tRC - whats the difference?

Discussion in 'Die-hard Overclocking & Case Modifications' started by BLEH!, Jun 17, 2011.

  1. BLEH!

    BLEH! Ancient Guru

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    Hey Gurus

    Maybe I'm being a little anal here but I'm doing what many of us do and trying to squeeze every last drop of performance out of my rig. Been faffing with RAM timings and some of the smaller numbers have me confused. I'm familiar with the normal 4 and can't seem to get any tighter where I am now (numbers to follow), but I'm wandering if faffing with any of the other timings with improve performance at all. Looking at CPU-Z though there's an odd thing, it might be a typo, I'm not sure, but I thought it work a check.

    Anyway, currently running Corsair Domi (3 x 2 GB) @ 1600 MHz @ 1.7 V. FSB 200 MHz, CPU 4.2 GHz, (x 21 multi), etc.
    Timings wise, under the "Memory" tab, this is whats confusing me, in comparison with the "SPD" tab. Highlighted the confusion in bold.
    My Memory from the "Memory" Tab:
    DRAM Freq: 800.0 MHz
    FSB:DRAM: 2:8
    CL: 7.0 clocks
    tRCD: 8 clocks
    tRP: 7 clocks
    tRAS: 20 clocks
    Row Refresh Cycle Time tRFC: 88 clocks
    CR: 1T

    and from the "SPD" Tab, XMP-1600 specs:
    Frequency: 800 MHz
    CAS# Latency: 7.0
    RAS# to CAS#: 8
    RAS# Precharge: 7
    tRAS: 20
    tRC:41
    Command Rate: 2T
    Voltage: 1.65

    I apologise for typing everything but I'm crap with HTML and have no idea how to embed pictures. So my main question is I guess, is tRFC and tRC the same and can I drop the 88 down to 41 in the BIOS for a performance boost?

    Either that or does anyone have any mad suggestions for improving performance by tweaking?

    Thanks

    BLEH!
     
  2. BLEH!

    BLEH! Ancient Guru

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    Anyone?
     
  3. Mufflore

    Mufflore Ancient Guru

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    Here you go, get the fix for your anal issues ;)
    http://www.anandtech.com/show/3851/...w-about-sdram-memory-but-were-afraid-to-ask/3

    Basically, memory contents must be refreshed or the data will disappear.
    This is done in banks of memory addresses.
    The time allowed to complete a refresh of a whole bank is tRFC.
    There is some safety margin to make sure that the job is finished so there may be room to tweak.

    This statement is key
    = from the start of a bank refresh, tRFC cycles are waited before it can be activated again.
     
  4. BLEH!

    BLEH! Ancient Guru

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    Cool, thanks
     

  5. Messerschmitt

    Messerschmitt Master Guru

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    Hi. I'm coming with the same question. Unfortunately I did not really understood Mufflore explanation.

    Actually my question is the following:

    Should I match the tRFC to the tRC in the SPD table?
    So if it says tRC in SPD 33, can I set the tRFC to 33?
    If not, how can I find the value?
     
  6. TechFreaK

    TechFreaK Banned

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    ^
    Hi,

    its not the same, tRC is ram's internal timing.

    http://www.tweakers.fr/timings.html#tRC

    tRFC affects ram read speed, higher vale = lower read, stabler operation.

    Im at 1092mhz - tRFC 82 (default is 70 at 1066mhz or 52 at 800mhz). DDR3 has higher tRFC 90-120+


    You can check Aida64 > go to motherboard > chipset >> scroll below for advanced timings. btw those that are missing could be risky, memset 4.1 doesn't show tRC either.
     
    Last edited: May 13, 2012
  7. Messerschmitt

    Messerschmitt Master Guru

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    Thanks. So is there a way to tell which is the tRFC number my memory supports? Unfortunately the SPD in CPU-Z does not provide that information
     

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