Asus P5B Deluxe Overclocking

[Anarchi]

I bought a new CPU and would like to overclock it properly.

The Mainboard is an Asus P5B Deluxe (i965 chipset, latest BIOS v1226).
The new CPU is a Core2Duo E6750 (2.66GHz, 1333MHz FSB)
The memory is DDR2 PC5300 (DDR667, 333MHz) Corsair ValueRAM


What I want is to increase the CPU to 3.2GHz, but keep the memory running at its stock 333MHz speed (being ValueRAM). So obviously I need to use an FSB:MEM ratio

I need to overclock the FSB from 333 to 400, but this will also increase the memory to 400MHz at 1:1 ratio. So I need to use a FSB:MEM ratio of 6:5 (400:333).


Now what confuses me is the Asus BIOS screen to change the ratio. Here is a screenshot:


It looks like the ratio's dont let you use a lower memory speed than the FSB speed, like you could with the Pentium 4's (The Abit IC7-G let you do it).

What option do I use to keep the memory at 333MHz when I overclock the FSB to 400? Or do I have to use DDR2-800 (PC6400) memory?

[SRTDodge05]

Leave everything auto and set the fsb to 333 like it needs to be. Then you'll be able to see where you need to set the boot strap.

[Anarchi]

That PC in the photo is not my PC, that PC is running a 266MHz CPU.

Mine is 333MHz, when I set the FSB to 333, it shows the same DRAM Frequency settings as in the photo.

When I overclock the FSB to 360, the memory also runs at 360. Its surprisingly stable at that speed (2.98GHz). But I dare not to go as high as 400MHz - ive overclocked performance memory before (expensive corsair XMS memory) and most sticks fail after a few months so I want to avoid RAM overclocking.


ps. As a test, I tried setting the DRAM Frequency up to DDR2-667, while the FSB was set to 300MHz. The memory was running quite high at around 376 and the PC was unstable (BSOD's). So those DRAM Frequency Ratio's only let you increase the RAM speed. I need a ratio that will 'decrease' the RAM speed.

It appears this Mainboard wont allow you to do this. Is this correct?

Is buying DDR2-400 memory the only option?