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Thread: The overclocking basics - help please

  1. #1
    Join Date
    Jan 2004
    Berkshire, UK
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    The overclocking basics - help please

    Hi all.

    I have read many things about OCing and wondered if someone could help with a brief look at what I know, what I don't and how to do it basically.
    I've never done it but am hoping to do so on my first new build.

    I would like to OC a P4 2.8 800FSB to 3Gz for instance.
    I will be using PC3200 DDR400

    I think it starts by raising the FSB of the CPU. This leads to an increase due to a calculation between the FSB and the multiplier (Which is locked on a P4)
    I know the FSB is quad pumped and so it would be a multiplier of 14? 14 X 200 = 2800 ? 214 X 14 = 3000 (ish)

    Soooo If I wanted a 3000 I would have to raise the FSB in the BIOS to 214 ??
    Is this right ?

    BUT because the FSB is somehow also linked to the memory frequency I have to up that as well to keep things in sync?? I would also do that in the BIOS I presume using 400Mhz from the DDR400 but to what value ?
    I plan to go for Corsair TwinX which I have heard good things about and might have heard that it would take a small increase it this right ? or should I really buy PC3500 "DDR420Mhz??"

    Geesh now I know why I am asking about this I am getting lost !

    Lastly isn't there something about the AGP and PCI being in a 66/33 lock ?? Can I keep this fixed and just forget about it.

    Many thanX

    P4 3Ghz @3.15Ghz, ASUS P4C800, 2X512MB Corsair TwinX PC3200, Sapphire Radeon 9800 Pro 128MB @ 390/370, 40GB Seagte, 2 X Vantec stealth's, Chieftec dragon.
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  2. #2
    Join Date
    Jul 2003
    0 times in 0 posts
    There are different ways of upping the FSB.
    The most popular way for small increases is to keep the fsb/mem ratio at 1:1 so that if you are running at 217 fsb then so is your mem.
    The other way is to run the fsb/mem frequncy at say 5:4, what this means is that if you run your fsb at 250 your mem will be running at 200 to keep it in spec.
    It works out like this: - your fsb (250) divided by 5=50 and multiplied by 4= 200. This way means that you can run tighter timings on your ram, but you will lose memory bandwidth due to the lower speed.
    On most P4 mobos you can lock the AGP/PCI to 66/33 to keep them in spec and avoid corruption.
    Hope this helps.

  3. #3
    Join Date
    Aug 2003
    0 times in 0 posts
    just passing by, sharing knowledge.

    Multiplier * FSB = Clock speed

    eg, 10x Multiplier * 100MHz FSB = 1000Mhz CPU

    .. so if u have a locked Multiplier u can (on most modern mobos) increase the FSB usually in 1Mhz increments.


    10x Multiplier * 101MHz FSB = 1010Mhz CPU

    this alters the PCI ratio thats linked to the FSB, the PCI bus "SHOULD" run @ 33Mhz so if your FSB is 100 then the ratio is 1/3 .. 1/3 of 100 = 33 ... this also goes for the AGP bus but it runs at 66MHz to the FSB is 100 and the ratio is 2/3 and therefore is 66MHz.

    If u have an unlocked multiplier u can use the multiplier to step up the CPU speed and therefore not affecting the FSB and also not affecting the PCI/AGP bus's. Oh and the whole affecting the PCI/AGP buses ... this rule applies for the RAM also!

    uhm.... thats the BASICS.

  4. #4
    Senior Member Kezzer's Avatar
    Join Date
    Sep 2003
    5 times in 5 posts
    phwoar you make it sound confusing. I just up the FSB to maximum suggested FSB in which my board can take it. That's it basically, i understand what OC'n' is but everyone seems to make it seem hard.

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