Nine times out of ten, it's the memory that holds you back. Plus, I think those boards like low voltage memory. I'm not saying to lower your voltage beyond spec though. If you can find a JEDEC 'figure' through CPU-z with your current ram, give it a try. I remember doing countless Memtest86 passes, p95 passes at 500fsb with a low multi and my DDR2 1000 kit. And then 4 months later after the system was pulled I put it back in and it was never stable. I think memory is very prone to failing and that may be your problem.
I used the 2.00B divider while at 400fsb and the rest of my settings on auto for 3.4Ghz and the vcore was auto'd at 1.28v on my Q9550
Let me see if I can dig up my old overclocking guide.... Ah, ok, revised. Here it is:
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Make sure you have the latest bios first of all.
Now, if you have all dimm slots occupied it will be alot harder running high fsb for something like 4Ghz... my 4Ghz is done by 500fsb by an 8 multi. I am running 2x2 & DDR2 1000 so I don't have to worry about hitting a memory wall when trying to overclock; thus 500fsb is my max without overclocking the ram. My Q9550 was almost near the Intel vcore max. In bios it was at 1.375 but with vdroop it drooped to a steady 1.34v.
First I would drop your multi to 6 and run Memtest HCI (500% or more) to see if your ram is stable at 1:1 ratio. So say if you have DDR 900 then 450fsb would be 1:1 and DDR 800 would be 400fsb at 1:1 and so on. This way you test to see if your memory isn't the problem. Mine was 6mulit x 500fsb = 3Ghz in windows. This way I knew there wasn't so much pressure on the CPU and RAM there-by isolating the motherboards subsystem. This is where you test the NB. I've switched to LinX and Super PI for testing stablitly. You can still use p95 for testing the NB by running Large FFTs.
A few settings I had:
**Clock Chip Control**
CPU Host Freq - 500fsb
PCI Express - 100
**DRAM Performance Control**
Performance Enhance - (I would keep yours at standard until you get a stable OC then play with this)
System Memory Multi - I was using 2.00D
>>> Standard Timing Control
Manually set these to the Memorys factory settings (mine were 5.5.5.15)
>>> CPU ***ALL OF YOURS IN THIS AREA MAY VARY FROM MINE***
Load-Line Calibration AKA LLC - Enabled
CPU Vcore - 1.37500v
CPU Termination 1.320v
>>> MCH/ICH
MCH Core 1.400v
>>> DRAM
Dram Voltage - 2.080v (my max is 2.1v - try keeping it under the very max)
MANUALLY SET THOSE VOLTAGES AT STOCK FIRST then raise them accordingly. You've eliminated your memory by testing your memory's Max advertised rating so that's when stuff like Vcore, Termination, and MCH Core come into play. There is a .0500 difference between the Vcore and Termination so try to keep that difference at all times.
You will probably pass Memtest HCI, LinX, Super Pi, & P95 Large FFTs at the lowest multi at your max 1:1 ratio and/or fsb.
So, when you start getting blue screens and or not booting into your OS, that's when you slightly raise those settings. PLL & MCH (MCH is your NB) would be a good place to start if you keep failing your boot or blue screen in any of the stablility testers; also raise your Vcore but keep that Termination at a difference of .0500v
With that, you should keep testing to you reach your OC goal. Be careful not to overheat your chip beyond 70*c on the cores. 70*c is conservative but good advice.
Have Fun and Good Luck!
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