Help me overclock!

Discussion in 'Overclocking, Benching & Modding' started by jepherz, Nov 13, 2011.

  1. jepherz

    jepherz Active Member

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    My rig:
    XIGMATEK HDT-S1283 cpu cooler
    EP35-DS3P gigabyte mobo
    Core 2 Quad Q9450 Yorkfield
    4gb DDR2 ram:
    OCZ2P800R21G
    CM2X1024-6400C4DHX

    First off, I'm confused about the ram. CPU-Z shows them as Max bandwidth "PC2-6400 (400mhz)" but in the bios I see 800mhz, is it 400mhz because I mix-matched my ram or is this normal? This rig is over 2 years old and has no stability issues, its never been overclocked yet.

    Is it important that I get the cpu:ram ratio to 1:1? It's at 5:6 stock right now according to CPU-Z.

    There is no unlink setting that I can find on the BIOs, I think I have to mess around with the memory speed multiplier but don't want to touch it yet... The CPU stock is at 333, if I increase it to 400 then I could change the memory speed multiplier from auto to 2 and it would leave the ram at 800 mhz and be 1:1 with my cpu. I don't want to jump right away to 400 though. It looks like everytime I change the number for the CPU the number for the ram changes too. Is there a chance the ram will become unstable if the number under or above 800?

    edit: that was probably very confusing to read... lets say I change the FSB of my cpu from 333 to 400, if I leave the memory speed multiplier on auto, I would have 960mhz ram, which I'm assuming means I'm also overclocking my ram. Or I could change the memory speed multiplier to 2 and it would be at 800mhz stock, but I would have to overclock all the way to 400 FSB to achieve this. I guess what I'm getting at is that I'm not sure if I want to be touching my ram like that, whether adjusting it up or down, but it seems linked to my FSB settings. I don't want to mess up my ram or anything and I'm not sure I even want to adjust my FSB all the way to 400 yet or if it will be stable. Core temps for me are higher than most people's for the same CPU... I idle at around 42ish with core 3 being in the 50s. These readings could be wrong though, they never seem to raise much when I play games that require a lot of CPU like starcraft 2...
     
    Last edited: Nov 13, 2011
  2. Takaharu

    Takaharu Unus offa, unus iuguolo

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    To address the RAM speeds, DDR2 6400 (800MHz) has a read speed of 400MHz and a write speed of 400MHz, thus giving a total bandwidth of 800MHz.
    As for the overclocking, I'll leave those recommendations to the pros.
     
  3. blibbax

    blibbax nahm8

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    I don't wish to suggest that I'm a pro, but here goes :p

    Ok, so yes, your FSB and RAM speed are linked. But this is normal, and it's fine. I think your instinct to not want to overclock your RAM is a decent one, but you needn't do so.

    You can think of the CPU speed and RAM speed as being functions of the FSB. At any given RAM speed that you can set in the bios, you will be setting a different multiplier, where FSB x multiplier = RAM speed.

    You don't need to worry about a 1:1 ratio between RAM and CPU - as long as the total FSB (e.g. 1333MHZ) is higher than the effective RAM speed (e.g. 800MHZ) and the RAM doesn't end up faster than you're happy with, you're fine.

    So here's what I'd recommend:
    -Set the multipliers such that your effective RAM speed is twice your FSB - e.g. 400MHZ FSB, 800MHZ RAM speed, as you mentioned. But leave the CPU at stock speed for now.
    -Make sure that the RAM timings are at their timings for 800MHZ, as opposed to 667MHZ - otherwise you'll be effectively overclocking the RAM quite substantially by undercutting the stock timings for 800MHZ.
    -Increase the FSB in small (5MHZ max) increments, testing stablity and temperatures as you go. I recommend a 10 minute run of Prime95 (set to max power consumption) as a basic stability test, and RealTemp as a temperature monitor. Keep an eye on the temperatures, if they pass 75 degrees (even if it takes them 30 minutes of Prime 95 to do so) you've gone too far.
    -If you encounter instability - maybe Windows doesn't load or Prime95 halts - but your temperatures are ok, you can try upping the voltages slightly. Don't go overboard - there will be a recommended voltage range for your chip on the Intel website's spec page for it. I'd stay (very) well within the maximum there.
    -When you get to a point you're happy with, stop. It doesn't matter if you've ended up with a RAM speed slightly under 800MHZ - this doesn't have anywhere near as much of an effect on performance as CPU clock speed. It also doesn't matter if you've ended up a few HZ over 800MHZ RAM speed - most RAM can tolerate a (very) small overclock.

    I should stress the usual disclaimers:
    -Overclocking can damage your hardware
    -Overclocking can shorten the lifespan of your PC
    -Overclocking can cause you to loose data or corrupt your Windows installation
    -Overclocking voids many warranties
    -Do not attempt to overclock without a suitable quality PSU, cooler and motherboard.
    -Overclocking (generally) makes your PC noisier and less efficient.
     
  4. jepherz

    jepherz Active Member

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    So about your first advice, I just want to make sure I got this right... I set my memory speed multiplier to 2 and leave the FSB at stock 333, that gives me 666 or 667mhz for the ram. Then I change the ram timings from auto to manual so I can set the default numbers for each 4 timings. My timings at stock are 5-5-5-18, so I set it to those numbers manually right? Then my ram would be running at 666mhz with stock timings, that's ok for step 1?
     
  5. blibbax

    blibbax nahm8

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    Yes, your RAM would be running at 667MHZ with the stock timings for 800MHZ.

    I think some motherboards will swap latency profiles automatically as you overclock, but obviously I've no idea whether yours does.

    Feel free to ask more questions, better that you understand thoroughly than that you break something :p
     

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