Tbh I'd start again from the beginning and try to establish the 'ceiling' overclock for each component in your system.
Lets break this down a bit. Your CPU can be overclocked by increasing the FSB, and if this causes instability then you may be able to rectify that by increasing the CPU voltage. Your FSB can also be increased, and if this causes instability then you may be able to rectify this by increasing the chipset voltage. Also, your RAM can be overclocked by increasing the FSB, and if this causes instability then you may be able to rectify this by increasing the RAM voltage.
Can you spot the link in the above?
They all involve increasing the FSB, so how are you supposed to know what caused the instability?
Well, the simple answer is you can't. Unless you take measures to eliminate the other components from causing the instability. This is where the multipliers come in
Dividers are just ways of increasing/decreasing the speed of components relative to others, and independently of the FSB. If you decrease the CPU/FSB multiplier, you can eliminate this from being the component that is causing the instability. If you decrease the RAM/FSB multiplier, you can eliminate the RAM from being the component that is causing the instability. If it's still unstable after decreasing these multipliers, then it's likely that the mobo is causing the instability, and voltage can be added to the chipset to try to increase the overclock.
Try this:
1) Set your RAM/FSB multi to around half of what it should be (i.e. 1:2 ratio instead of 1:1);
2) Set your CPU/FSB multi to around half of what it should be (i.e. 3x or 4x, instead of the usual 7x)
3) Try increasing your FSB in 5 or 10 Mhz increments and stability test between. If you experience instability, increase the chipset/NB voltage and try again. If it's stable, continue to increase the FSB. Keep doing this until you find a stable ceiling. Keep a log of all the FSB's and voltages and whether it was stable or not.
4) You now know what the max FSB is that your mobo can handle. Put the FSB back to stock, set the CPU multiplier back to 7x and start overclocking again. This time, keep your chipset/NB voltage inline with the notes you made for the frequency it's running at, and increase the CPU voltage if you get instability. Keep doing this, increasing in 5 or 10Mhz increments until you find the stable ceiling for the CPU. Keep a log!
5) Set the CPU multi back down to 3x or 4x. Set the RAM multi back to 1:1. Start increasing the FSB, chipset/NB voltages once again in line with the log you made, and increase in 5 or 10Mhz increments until you find the stable ceiling for the RAM.
6) You should now have the max stable overclocks for each individual component, so now you need to try to work all of them together by calculating the frequencies and dividers to try to get the best compromise for them all. Prioritise on the CPU speed first.
I hope that helps
And btw, I'm an Athlon64 overclocker so if I've made some fundamental mistakes in the nature of overclocking Core2Duo's then please somebody feel free to correct me
