Question on P45 Platinum bios setting for "Adjust PCI Frequency (MHz)"

Question

System:
P45 Platinum updated to bios 1.6
Intel Q9400 CPU with Xigmatek Heatsink
620W PSU
8BG (2x4 slots) Cosair TWIN2X4096-8500C5D PC2-8500 1066MHz
PowerColor 1GB ATI HD 3670 Video card
System runs almost fine at the default setting.  As it boot to blank screen a few times.  Hard reset to boot into system fine.  Once a while, system just froze and need hard reboot.  But seem to stable enough (temperature around 26C)
I wanted to overclock to 3GHz.  But as I just increased FSB from 333 to 340, the system will not boot or it will boot and then locked up after logon to window.   I left everything at auto.  Do I need to set the PCI clock?  It is default at auto.

Answer 1

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I have to constantly change the FSB/Dram ratio to keep the RAM frequency between 800-900 for it to stable.  Otherwise, the system will reboot by itself. Is that because I used all four slot of RAM?
Well, the fact that all memory slots are populated makes the matter a little more complicated, but the main problem is elsewhere:  The Intel P45 Chipset natively only supports DDR2-667 and DDR2-800 modules.  In addition to that, your memory modules are not "real" DDR2-1066 modules, but DDR2-800 memory sticks with a permission to overclock and overvolt them to DDR2-1066 @~2.1V. 
Try these settings to try to raise your memory clock speed farther:
- Enhance Setting (Try all settings here: "Enabled", "Disabled" and "Auto")
- DRAM Voltage = 2.1V
- DDR_VREF_A = 0.955V
- DDR_VREF_B = 0.955V
- Spread Spectrum = Disabled
Usually, the reduction of the DDR Reference Voltages compensates stability problems that are related to overclocking/overvolting the memory to DDR2-1066 on this board.  There is no guarantee that it will work for you, but you may as well give it shot.
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Everything else is auto and Core Center is showing:
vcore 1.21v
memory 1.92v
nb 1.12v
CPU temperature after an hour of usage: 23C
You don't wanna use MSI Dual Core Center for temperature monitoring.  The tool is unable to read/calculate the Core Temperatures of your processor which are based digitial sensors implemented in each processor core.  The data these sensors collect is stored in specific CPU registers that can be accessed by tools like Core Temp, Real Temp, Everest Ultimate and Speedfan (there are more tools of course).  The "CPU Temperature" value shown in BIOS and by MSI Dual Core Center are based on the readings of an analog sensor of unknown location.  It is uncertain, what this value actually refers to and it is also not very reliable.