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  1. #1
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    Jun 2006
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    Underclocking Aopen Ak77-333 motherboard to support 333Mhz FSB AMD processor

    Hi guys,

    I currently own an AOpen AK77-333 motherboard and want to upgrade the processor as my old one fried. It says on the AOpen web site that the KT333 chipset on the motherboard can support 333MHz FSB but the max the motherboard can support is 266MHz. I want to go with an AMD Athlon XP 2600+ thoroughbred processor with 333Mhz FSB(only one I could find at a decent price). So now my question is can I run that processor on my motherboard as is? Or do I have to underclock the FSB on the processor to support my motherboard. Or am I just SOL. Thanks for the help.

    Also maybe one thing I should note is that I did a BIOS upgrade to support the thoroughbred processors. Im not sure if it supports all of them or what then?

  2. #2
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    Re: Underclocking Aopen Ak77-333 motherboard to support 333Mhz FSB AMD processor

    Hi Hecilopter, welcome to PCPer

    http://global.aopen.com.tw/Products/mb/ak77-333.htm

    According to that page, CPU FSB support is only up to 266MHz, so no - a 333MHz AthlonXP 2600+ won't run at the full 333MHz. I wouldn't trust it even at underclocked speeds. There's a CPU support list on the link above. 333MHz CPU's aren't included. Sorry.

    The VIA KT333 chipset does support 333MHz, but it needs BIOS support for that to work. In your case it looks as though AOpen have moved on and forgotten about that board. There may be after-market BIOSes you can try, but that's murky water. There's no guarantees there either. Not worth a punt if you're skint on cash.

    You'd be much better off buying a new mobo and CPU.
    Last edited by Mjölnir; 06-06-2006 at 09:43 PM.

  3. #3
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    Re: Underclocking Aopen Ak77-333 motherboard to support 333Mhz FSB AMD processor

    Are we getting confused over fsb speed-doubling here? A "333MHz fsb" Athlon is actually running at 166MHz: Athlons have run at 100, 133, 166 and 200MHz only. It's just that some publicity refers to the DDR rate of 333 instead. When the motherboard says that it will run up to 266MHz, it means an actual 266MHz, not a speed-doubled 266 (i.e. actually 133). Thus your Athlon will work fine as long as you set the m/b to 166MHz fsb. The board may not run 200MHz chips though that is what VIA's KT600 chipset was for. Look at this and then divide the fsb and RAM speeds by 2 to get the real figures.


    M

  4. #4
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    Re: Underclocking Aopen Ak77-333 motherboard to support 333Mhz FSB AMD processor

    Quote Originally Posted by Meridian
    Are we getting confused over fsb speed-doubling here? A "333MHz fsb" Athlon is actually running at 166MHz: Athlons have run at 100, 133, 166 and 200MHz only. It's just that some publicity refers to the DDR rate of 333 instead. When the motherboard says that it will run up to 266MHz, it means an actual 266MHz, not a speed-doubled 266 (i.e. actually 133). Thus your Athlon will work fine as long as you set the m/b to 166MHz fsb. The board may not run 200MHz chips though that is what VIA's KT600 chipset was for. Look at this and then divide the fsb and RAM speeds by 2 to get the real figures.


    M
    I don't think anyone was confused on that front Can I clarify what you said? I interpreted that as suggesting that the board is capable of running a 333MHz FSB CPU, which it's not designed to do, acording to the AOpen site.

    It's industry standard to refer to FSB in publications and press by it's DDR frequency [200/266/333/400MHz]. AMD do it, VIA do it, NVIDIA do it, etc. It's less common for publications to refer to FSB by it's "single data rate" (SDR) frequency [100/133/166/200]. As I see it, the confusion exists because many (probably most) motherboards list FSB in their BIOS options by it's SDR frequency [100/133/166/200] - not it's DDR frequency as mentioned in the majority of official publications.
    Last edited by Mjölnir; 06-07-2006 at 12:08 PM.

  5. #5
    Joined
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    Re: Underclocking Aopen Ak77-333 motherboard to support 333Mhz FSB AMD processor

    And since there isn't even a 266Mhz FSB CPU (if that would mean 533Mhz), why would AOpen officially support that with a KT333 chipset.

    But if the BIOS doesn't support a speed over 133Mhz FSB, maybe the clockgenchip used on the board still does. You could try to use a tool in windows to change the FSB to 166Mhz in that case and most of those tools also have some way of applying that FSB everytime you restart your computer, so u dont have to do it yourself everytime.
    Just make sure your memory divider is set to 1/1, 1:1, 100% or 266Mhz because if the FSB is running at 133Mhz and the memory at 166Mhz (DDR333) and u increase the FSB speed (and there by memory speed) in windows, the memory controller in the KT333 will probably crap out.
    Overclocking system:
    ASUS Rampage Formula (BIOS 0403)
    Xeon x3350 SLAX2 @ 8x475=3.8Ghz 1.29Vcore
    Dual Radiator (modded) Koolance EXOS with Zalman WB5 CPU block
    2 x 2GB OCZ Platinum PC8000 @ 950Mhz 5-5-5-18 1.8v
    Enermax NoiseTaker 600W
    ASUS GeForce 8800GTX @ 645/1645/1000

  6. #6
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    Re: Underclocking Aopen Ak77-333 motherboard to support 333Mhz FSB AMD processor

    On request, I have just re-read this. I was partly confused myself, but it goes like this:

    The board can supply any fsb up to a real fsb of 333MHz, BUT, the on-board PCI divider only goes to 4:1. This means that 133MHz (or 266MHz if you follow AMDs marketing ploy) fsb Athlons will correctly run the PCI slots at 33 and the AGP at 66MHz. If you dropped in a 333MHz chip (real fsb = 166) like the OP suggested, then the board would run it at 133MHz. The PCI and AGP slots would be just fine, but the CPU would be running at 133/166 x real speed - effectively an underclock. This wouldn't harm either board or CPU, but would be a waste of CPU speed.

    Now the CPU is almost certainly locked, so the OP can't just raise the multiplier to compensate, so the only other alternative would be to raise the fsb. But since the PCI bus is a) not fixed, and b) running a max of a 1/4 divider, you then get all the attendant issues of running an out-of-spec PCI bus. KT400 was mainly brought out to introduce the 1/5 divider for 166MHz bus cips like the OP's, and KT600 for 200MHz chips.

    Short answer: yes, it would almost certainly work, albeit at the cost of the CPU running underclocked as you said. The only problem might be the BIOS having a hissy fit a the CPU.


    M

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