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Thread: Please help: Does not boot after BIOS setting change

  1. #1
    Join Date
    Jan 2009

    Default Please help: Does not boot after BIOS setting change


    I have Pentium 4 CPU 2.4 GHz, with 800 MHz FSB
    The mobo is D875PBZ (Intel® Desktop Board D875PBZ - Intel® Desktop Board D875PBZ support)
    RAM is DDR 400

    I was trying to figure out why system memory speed in BIOS is 266 MHz.
    I found the following BIOS settings in

    Advanced --> Chipset Config --> Memory
    SDRAM Timing Cntrl [Manual - User Defined]
    CRC Override [Auto]
    SDRAM Frequency [266 MHz]
    ...and other numbers for the memory

    I thought that since the PC came with manually overriden clock speed of 266 MHz for memory, I wanted to see if setting it to Auto would clock the memory at 400 Mhz (effective)

    So I changed the SDRAM Timing Cntrl to [Auto], and pressed F10 (save and exit).
    Since then screen went blank, and I can't boot (tried multiple times)

    Please help. What should I do?


  2. #2
    Join Date
    Nov 2001
    Texas, USA

    Default Re: Please help: Does not boot after BIOS setting change

    Check out the motherboard manual (or search for it online if you don't have it handy) and locate the CMOS reset jumper. Should be three pins with a 2-pin jumper block on it. Move the jumper block to the opposite side of the block and let it sit there for several seconds (some motherboards longer than others... go drink a cup of coffee). Replace the jumper to its original location and reboot. The BIOS should have reset to default settings, which will generally boot using an auto-configuration routine that looks at your hardware and uses standard settings.

    Once you have that completed, keep in mind that during the time your board was manufactured, Intel featured pretty much NO overclocking capabilities in their product line. The only reason they had any adjustments at all was for flexibility in the range of supported processor and memory configurations.
    Old age and treachery will overcome youth and skill
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  3. #3
    Join Date
    Jan 2009

    Default Re: Please help: Does not boot after BIOS setting change

    Thanks. I will try that.

  4. #4
    Join Date
    Jan 2009

    Default Re: Please help: Does not boot after BIOS setting change

    Thanks for the help.
    I set the BIOS jumper for my mobo (D875PBZ) in "configure mode" and powered on, thereby forcing it to enter BIOS.
    It looks like this mobo has issues with setting the timings by "Auto" mode and letting it get the values from SPD. It doesn't even POST.
    I forced the BIOS memory timing setting back to "Manual - User Defined".
    But this time, I set the timings according to SPD, i.e., 3-3-3-8, then put the jumper back in "normal mode" and powered on, and it booted. So far so good.
    I don't know why my friend (who gave me the old PC), or his vendor, had set it manually to 2-4-4-8 with 266MHz (effective).

    (One thing I learnt though from the datasheet of Elpida Chips EDD2508AETA making up my Kingston Value RAM KVR400x64C3A/512 is that it can support a tCL of 2 at 133MHz (effective 266, as was set earlier in my BIOS), and a tCL of 3 at 200 MHz (effective 400MHz) and a tCL of 2.5 at 166 MHz (effective 333 MHz)

    After knowing how to come back to 'working' settings, I found out on (AnandTech: Value RAM Roundup: Computing On a Budget ) that I could run this RAM even at 2.5-3-3-6 at 400 MHz. So I am doing that right now. So far so good again.

    I know that for a given frequency, lesser the timings, the better.
    But just out of curiosity, which one of these is better?
    3-3-3-8 at 400 Mhz
    2-4-4-8 at 266 MHz?

    (I know probably for a non-gamer like me, the difference in performance won't be noticeable, but neverthless, which setting is better?)

    Thanks a lot again for your help.

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