change the ratio and take the ram out of the equation to see if it posts
Sorry what do you mean Easy?
Just been looking around have come across this article:
For the i965 chipset to stand a chance of hitting high FSB speeds some clever manipulation of the chipset internal timings are needed. Most know Intel release CPU's with various default FSB speeds, the usual suspects are 533, 800 and 1067. Celerons are usually fixed on the 533 bus but should be moving soon to the 800, most other P4 775 CPU's are 800 bus speed apart from the older Extreme Edition and the new C2D CPU's that are based on the 1067FSB.
The CPU has a set of pins or dots on the base called the BSEL . These pins or dots actually tell the board what FSB to apply to the CPU and tell the chipset what strap to run. The strap is actually a set of ram ratio's and a clock muliplier along with an internal latency setting. Try to think of the northbridge pretty much like a CPU...it uses a default frequency and a muliplier..and yes you can overclock it.In difference to a CPU though it also controls the memory and as such has internal latency settings that can be changed also.
Now....what you have to remember is as you push up the FSB on the CPU you also push up the FSB on the chipset. By default the chipset hits its max clock way before the CPU does...so what do you do?
The answer is manipulate the chipset into thinking it is working with a CPU that has a higher FSB default speed.
How this is done is by altering the BSEL signals the chipset uses and by setting the undocumented(at this time) 1333 strap...this means the chipset thinks it is working with a CPU that has a base FSB speed of 333 (quad pumped is 1333)
Now Asus have been quite slick with the P5B range of boards as they allow the chipset to overclock quite a bit before they slow it down by altering the strap, what this means is that once slowed down by the 1333 strap it is already in an overclocked state. The bad part is that between 360 and 399fsb the chipset is massively overclocked and really does struggle some what, the consequence of this is an "FSB hole" where it is hard to get the board stable. In reality all you have to do to avoid this "hole" is set 400fsb or higher as the strap changes here to 1333 and the board takes off again usually all the way to 500+FSB. I explain more on what exactly is happening here in more detail.
What would be nice is the 1333 strap coming in at 360FSB but with the internal latency set using the 1067 strap which is faster than the 1333 latency setting, this would allow the board to work well up towards 399FSB.from 400FSB you would relax the latency setting to the 1333 default and allow the board to clock all the way to 500+ without the non usable hole we see at this time. hopefully if Asus see this article they will tweak the bios to set more like what I have quoted...but for now the board is an awesome overclocker as it is by default but it has this 1 quirk.
I sort of understand it but not fully.
