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Would a 533 Mhz FSB processor work in a 400 Mhz motherboard?

Discussion in 'Intel' started by Buck Rogers, Apr 26, 2006.

  1. Buck Rogers

    Buck Rogers Guest

    Hi all!

    Will it scale down to 400 Mhz, or won't it work at all?

    I am asking because the fastest CPU that my machine can
    take is P4 2.6 Ghz, 400 Mhz FSB. But I am having trouble
    finding 400 Mhz FSB cpus, whilst there are plenty of
    533 Mhz FSB cpus on ebay.

    There are even Xeon 2.2 Ghz, which run at 400 Mhz FSB,
    but somehow I don't think my old Dell Dimension 2350
    can run a Xeon! It came with a 2.2 Ghz Celeron.

    Thanks in advance!

    Buck Rogers, Apr 26, 2006
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  2. Buck Rogers

    Buck Rogers Guest

    Buck Rogers, Apr 26, 2006
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  3. * Buck Rogers:
    So what? Just having the same chipset means zero. The point is if the
    BIOS of your Dell will accept the unsupported CPU, and even if it runs
    it probably lacks the proper microcode for it...

    Benjamin Gawert, Apr 26, 2006
  4. Buck Rogers

    DaveW Guest

    No you CANNOT use a 533 MHz bus CPU in a 400 MHz bus board. (RAM sticks can
    run at lower speeds safely, but CPU's cannot.)
    DaveW, Apr 26, 2006
  5. Buck Rogers

    Nate Edel Guest

    That depends on how you mean "cannot run at lower speeds."

    I've underclocked CPUs just fine, many times, without any problem, including
    - purely to see how it would run, my new Pentium D - which runs quite
    happily at 2128mhz rather than 3200. That said, with modern CPUs (P4s,
    Athlons) that has been via board settings on boards that support a given
    CPU, *not* via plugging a CPU into an older board that didn't support the

    And back in the Slot 1/Socket 370 days, it was often (depending on the
    individual chipset/motherboard combination) safe to run a 133mhz or 100mhz
    FSB chip in a board that only supported 100mhz or 66mhz (don't recall ever
    seeing a 133mhz chip tried in a 66mhz board, though!)

    I knew a guy who ran a 133mhz chop (a P3/800, IIRC) at 100mhz most of the
    time, since the BX chipset wasn't officially spec'd to run at 133mhz.
    He'd normally run it underclocked, and then reboot and switch it up for
    playing games.
    Nate Edel, Apr 27, 2006
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