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Old School question : Pentium III 800 underclocking

Discussion in 'Overclocking' started by [email protected], Feb 5, 2007.

  1. I have an old motherboard by pcs, p6set-ml , and it has a socket 370
    and a slot one on it. There is no voltage jumper. You configure the
    FSB and the multiplier in BIOS. I can set the FSB to 100 and mult to
    8.0 to achieve a speed of 800 MHZ. It will accept FCPGA Socket 370
    chips (celeron and pent. III).

    These day's, used PIII FSB 133 chips are CHEAPER than used PIII FSB
    100 chips. Wouldn't it be completely possible to put a 133 FSB rated
    PIII into a board that only produced an FSB of 100? Isn't the voltage
    spec and the pysical package spec the same? It seems that the chip
    wouldn't know the difference...

    Any response is appreciated... thanks.
    [email protected], Feb 5, 2007
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  2. Yes, I believe that is correct - however, in those days, I was more in the
    AMD camp.

    What I am sure of is that you will only reach 3/4 of the CPU's rated speed,
    unless you are definitely able to change the CPU multiplier (i.e. if your P3
    is unlocked).

    John Whitworth, Feb 5, 2007
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  3. in regard to my earlier post ...

    This is table data from Excel copied from a processor analysis webpage
    by Intel, and you'll notice wrap around for some browsers... etc...
    The link to the intel website is:

    SL463 800 MHz N/A N/A 100 MHz 0.18 micron CB0 256 KB
    370 pin
    SL4MA 800 MHz N/A N/A 100 MHz 0.18 micron CC0 256 KB
    370 pin
    SL3Y3 800 MHz N/A N/A 100 MHz 0.18 micron CB0 256 KB
    SL4CE 800 MHz N/A N/A 100 MHz 0.18 micron CC0 256 KB
    370 pin

    In regard to my previous post, several processors were produced which
    specifically adhere to the 100mhz fsb, pIII, 800mhz spec... I want my
    processor to fit into a socket 370, yet not "lock" the FSB rate and
    allow the bios to modify it... which stepping would that be? I'm
    guessing CB0 FC-PGA ... "flip chip"? Because that was the early one
    with no "clock locking"?

    I'm guessing SL3Y3 (flip chip) at best, or SL463?

    SL3Y3 is very expensive at pricewatch.com... and likewise for SL463.
    ebay too...

    Based on my previous post, Is it more expensive in the secondary
    market because they know it is "flexible" and not "clock locked"?
    Less produced?

    Any feedback and curiosity is appreciated... thanks.
    [email protected], Feb 6, 2007
  4. ....@m

    Ed Medlin Guest

    All the P3 (with exception of a very few engineering samples) processors had
    the multiplier locked. Many MBs had the option to change the FSB. The reason
    the 100mhz 800s were popular was because they would almost always run at 133
    for 966mhz and usually without problems.

    Ed Medlin, Feb 6, 2007
  5. [pedant mode] 8 x 133 = 1066, not 966, and this was not a guaranteed
    overclock in most cases.

    It was the P!!! 700MHz parts that were regarded as "sure things" at 133MHz,
    which gave you a 933MHz CPU.

    [/pedant mode] ;-)


    Richard Hopkins
    Cardiff, Wales, United Kingdom
    (replace nospam with pipex in reply address)
    Richard Hopkins, Feb 8, 2007
  6. Yes, the four different stepping codes you list are the retail and "OEM"
    versions of the two different stepping codes produced.
    Eh? *None* of the Coppermine CPU's are able to "lock" the FSB clock.
    However, all retail Pentium!!! CPUs contain a locked *multiplier*. Your
    motherboard may offer you the option of changing the multiplier, but you
    will find that actually doing so has no effect. Whatever you set in there,
    the CPU will run at whatever FSB you set times its own onboard multiplier.
    You seem to be mixing your terminology here. All four of the CPU step codes
    you quote will have a locked 8.0x multiplier. However, none of them "locks"
    the motherboard's FSB clock at 100MHz.
    The only reason I can think of for the cB0 chips being more expensive
    secondhand is that they used to run cooler and tended to overclock a little
    better than the cC0 stepping parts. You are incorrect in thinking that the
    earlier parts are not "locked" and the later ones "are", they are all equal
    to each other in that respect.

    As Ed has already mentioned to you, the only way you can overclock or indeed
    underclock a retail Intel processor of the age you are talking about is by
    raising or lowering the FSB relative to its default speed. In order to do
    that, you need a motherboard that offers FSB adjustment.
    You can do it, but if you did so, the CPU would run at only three quarters
    of its rated speed. In other words, bung a Pentium !!! 933 CPU in a board
    that only runs 100MHz FSB, and you end up with a CPU running at 700MHz.
    Yes, provided you are talking about Coppermine Pentium!!! CPUs. When you get
    into the Tualatins, the physical socket spec and VID (voltage settings) are
    The chip doesn't "know" the difference, it just runs at whatever FSB you
    feed it times its own internal multiplier. As such, if you can't alter the
    FSB on your own motherboard, you are very limited in what you can do,
    unless, as mentioned by Ed, you are able to find an Engineering Sample CPU
    with an adjustable multiplier.

    Richard Hopkins
    Cardiff, Wales, United Kingdom
    (replace nospam with pipex in reply address)
    Richard Hopkins, Feb 8, 2007
  7. ....@m

    Ed Medlin Guest

    LOL............yup. It was a 700 I was thinking of. Damn, it is tough
    getting old. ..........:)

    Ed Medlin, Feb 9, 2007
  8. Thanks for the update. My terms are "off"... sorry. Yeah, the
    motherboard offers 66 or 100 fsb set in bios, with a max mult. setting
    in bios of 8.0 to attain 800 mhz. This motherboard accepts either
    slot 1 or sock. 370 processors of PIII/PII or celeron types (The
    flexibility in the bios for setting the mult. must be for the celerons
    and PII's, etc... )

    So, I'll have to adhere to getting a 100 mhz rated PIII (as you said,
    a 133 would run cut rate)... Thanks for the info.
    [email protected], Feb 9, 2007
  9. ....@m

    ~misfit~ Guest

    I have no trouble at all. I just sit here and it happens. <g>
    ~misfit~, Feb 12, 2007
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