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Slower FSB BSEL Mod?

By AdriMagnon
Jan 21, 2009
  1. Hi,

    I have a motherboard with the Intel 945G/GZ chipset, according to CPU-Z 1.46, and my Processor is the Intel Pentium 4 521 Prescott 775 90nm 2.8 GHz (14x200) Stepping 1, Revision E0 processor. I read about the BSEL Mod and VID mods but since I can't unlock the multiplier the 3.7 GHz (14x266) will probably be too much for then chip with only air cooling. However I read that 3.4 - 3.6GHz is a good spot for this processor so how would I do a BSEL to only 1000 FSB (250)? Is this possible? I've seen the BSELs for 800 -> 1066 and 800 -> 1333 so I assume there is a 800 -> 1000. I looked at a PDF Whitepaper on the BCLK table only shows the 200 MHz BCLK. It doesn't say what the other combinations would do.

    I'd also be happy with FSB 933: FSB 233 x 4 = 932 = 3.26 GHz

    Also, the motherboard does not support overclocking via the BIOS so this would be my only way. I can get my hands on 1066 RAM or even 1000 RAM if needed.

    Please let me know and I appreciate any help you can give.


  2. vnf4ultra

    vnf4ultra TechSpot Paladin Posts: 1,388

    Since there was no official FSB speed between 800 and 1066, I don't think it's possible to do what you are wanting.

    Cpu's multipliers can be adjusted down, just not up, even if they're not unlocked. I'd say if you can change the multi in your bios (low end boards might not have the option), then try a 13x multi and 266 (1066) FSB (bsel mod), as that'd be right in your "sweet spot" of speed.
  3. AdriMagnon

    AdriMagnon TS Rookie Topic Starter Posts: 20


    Unfortunately my BIOS doesn't allow under-multiplier-clocking. I was looking on a several sites and one (xtremesystems.org/forums/showthread.php?t=132900&page=4) posted the following:

    L L L 266
    L L H 133
    L H H 166
    L H L 200
    H H L
    H H H
    H L H
    H L L 333

    I was looking at it and realized that the three open options could be 100, 233 and 300.

    H H L
    H H H
    H L H

    I am thinking this because it would 'fill in' the run from 100 to 333. I mean we'd get, assuming the site was right,...

    (100), 133, 166, 200, (233), 266, (300), 333

    Does this look right or make sense? I would guess that H L H would be 100. I base this off of how 166 = L H H which is 1/2 of 333 which s H L L. To go from 166 to 333 each H/L just flips to the opposite. However, I see inconsistencies with this idea because by then looking at the hundreds field it looks like 300 Starts with BSEL2 H, under 300 starts with BSEL2 L, and the 100s start with BSEL2 L but BSEL0 H. Any ideas?

    Also, I was looking on the whitepaper but can't see a way to lower my multi without the help of the BIOS. I haven't looked at the Intel 945 chipset data yet -- maybe I can do a pin mod on that to force the multi lower.

  4. vnf4ultra

    vnf4ultra TechSpot Paladin Posts: 1,388

    I don't think the three undefined BSEL combinations would have any meaning, because they are just that, undefined. I could be wrong, but I'm under the impression that since intel never used these parameters, then likely setting a cpu to those values would be seen by the board as an invalid configuration.

    IMO, you need a new board if you want to oc your cpu.
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