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Socket A compatibility and FSB speeds

Discussion in 'AMD Overclocking' started by Whoever, Jan 4, 2005.

  1. Whoever

    Whoever Guest

    Q: Will the XP processors run at lower FSB speeds than the rating?

    Explanation: I have a MB with 200MHz FSB and possibly a spare Athlon-XP
    1800 (266 MHz FSB)

    The XP 1800 processor is currently running in a Soyo KT333 Dragon Lite,
    but I am wondering about replacing it with an XP 2600+ and then putting
    the XP-1800 in the system which has the 200MHz FSB and is currently
    running a Duron @1GHz.

    Any thoughts?
    Whoever, Jan 4, 2005
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  2. Whoever

    Wes Newell Guest

    They're rated for a FSB of 50MHz, but should run at a lower speed. I
    haven't found a MB that will even get down to 50MHz though much less
    lower. What I think you meant to ask was if they'd run at a lower speed
    than the default and the answer is most definately yes. They'll also run
    at much higher speeds.
    Nope the 1800+ uses a default FSB speed of 133MHz, not 266MHz. It's called
    a 266FSB for marketing BS. See The Real Front Side Bus in link in sig
    line. Most MB's that say they support a 200MHz FSB probably refers to the
    real speed of 200MHz. That would be 400FSB.
    This Duron only uses a 100MHz FSB. Now if you mean your other board
    supports a 200FSB (100MHz) then the 1800+ will not reach it's default
    speed without raising the multiplier from 11.5 to 15 or 16.
    Wes Newell, Jan 4, 2005
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  3. Whoever

    Whoever Guest


    Yes, you are correct. I was using the marketing numbers. So I have an
    XP-1800 which has a DDR interface at 133MHz (marketing rating = 266MHz
    FSB) and I want to know if it will work in a MB which only supports a FSB
    at 100MHz/DDR (marketing rating 200MHz). According to your website, it
    should, but the processor will run a little slow (more like a 1400+:
    1800/1.33 = 1353).

    I also want to know if I am limited to using the XP 2600+ processor in the
    board that currently has the XP-1800+ and has the 133/DDR interface
    (marketing FSB rating = 266MHz), or if I can actually use a faster
    processor -- even if it does not run faster. For an explanation of the
    question, look at the prices of the 2600+/266 processors -- they seem to
    have rarity value pricing!

    Again, your website seems to read that again, this is possible, but the
    processor will run slow, because the maximum multiplier is locked within
    the CPU -- if I understand it correctly, a 2800+ processor (for example)
    would run like a 2200+ processor (2800*133/166 = 2243)

    Am I correct in my calculations?
    This would actually be quite a nice option for me -- the computer runs
    100% of the time, so an underclocked XP might run cooler and hence
    be more reliable than a duron at full speed (while still being a more
    powerful processor).
    Whoever, Jan 4, 2005
  4. Whoever

    Wes Newell Guest

    The 1800+ XP will run at 1150MHz (11.5x100) unless you can change the
    multiplier or raise the FSB. Even the earliest boards that only supported
    100MHz FSB can usually be raised to about 115MHz, bios/jumpers permitting.
    I could get both my KT133 boards to 116MHz. If you have an unlocked model,
    or an old Palomino core you can unlock, you can change the multiplier to
    whatever you want.
    If I had a board limited to 133MHz FSB and wanted max possible speed, then
    I'd look at getting a 2400+ XP-M. You should be able to set this up to a
    minimum of 2250MHz. Otherwise, the extra $7 they want for a /266 model
    2600+ doesn't seem that bad to me ($69 vs. $76).
    AFAIK, All XP-M's and MP's are still unlocked and can be set to any valid
    multiplier up to 24x.
    Wes Newell, Jan 4, 2005
  5. Whoever

    Whoever Guest


    Since the 1800+ does not actually run at 1.8GHz, this is fine. An XP
    running at 1150MHz should be faster than a Duron at 1.2GHz. (stated max
    processor speed for the board).

    I have not seen anyone selling an XP-2600+ for $76 -- can you give me a
    This is interesting info.

    Wes, many thanks for your informative replies.
    Whoever, Jan 4, 2005
  6. Whoever

    Bushy Guest

    Sorry to hijack the conversation, but something Wes said interests me, or
    perhaps i just misinterpreted it.

    Did you say that a xp-m would run at 133MHz FSB (ie 266)? i have an a7a266-e
    downstairs running a xp1700+ and i've been trying to figure out a way to get
    a cheap, noticable upgrade. could an xp-m be stuck in this board and then be
    setup to run stable? at 133*17=~2200Mhz (for example) would give a decent
    old whack.

    Be glad to hear comments from anyone

    Bushy, Jan 5, 2005
  7. Whoever

    Wes Newell Guest

    Wes Newell, Jan 5, 2005
  8. Whoever

    Wes Newell Guest

    The XP-M will run at any FSB you set it to. Default of all XP-M and MP
    cpu's is 133MHz afaik. You can verify this by the PN ending with a C. I
    don't know anything about your board, but it should support the XP-M. Easy
    enough to find out. Just change your XP to an XP-M by closing a bridge or

    Wes Newell, Jan 5, 2005
  9. Whoever

    Whoever Guest


    But did you see the feedback for the person selling at $76? Fortunately
    someone with better feedback is selling at $78
    Whoever, Jan 5, 2005
  10. Whoever

    Christo Guest

    a 2800 processor will only run at 2 ghz or there about, a 2600 will run at
    1.9 a 3200 will run at 2.2, all AMD top end processors run at 2.2 ghz, even
    ..3400, that is apart from FX processors some of which hit 2.4ghz and 2.6ghz

    but the mere model name AMD XP Athlon 2600+ doesnt mean its a 2.6 ghz
    processor, its just the model number, the way you calculate the speed of a
    processor is go to the BIOS

    find the FSB

    for my 2600+ the fsb should be 166MHz

    then the multiplier, which i believe i have at 11.5 or maybe 12

    anyhow if you take the multiplier

    11.5 and multiply it by the FSB 166

    11.5*166=1909 thats the processor speed in MHz

    so say you have an FSB of 100 MHz and a multiplier of 10 then the speed
    would be of cource 1000 MHz or 1GHz
    Christo, Jan 6, 2005
  11. Whoever

    Ed Guest

    Not to nitpick or anything but, the correct calculation would be
    166.66 * 11.5 = 1916.59MHz (Barton 2600+)
    Ed, Jan 6, 2005
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