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Corsair XMS2 Tweaking Unstable

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Hello. I'm new to overclocking and have been trying to bone up on it.


3 days ago, after months of pondering my best path, I moved up from a P4 2.8 Prescott to a Core 2-based rig. I had wanted an E6600, but a friend talked me into waiting for the quad cores to arrive. So I got a QX6700, along with an Asus P5B MB and Corsair XMS2 DDR2-800 memory.


I haven't OC-ed in the past, mainly because the MBs I owned were all included in the systems I purchased as a unit, and they don't offer such tweaking options.


Getting to the point of this topic, I followed the Ram Guy's advice on BIOS settings for another user who had a similar Asus MB:


AI Over Clock Tuner: Manual

CPU External Frequency: Manually set to 266MHz

DDR2 SDRAM Clock: Manually set to 800MHz

PCI Express Freq: Auto

PCI Freq: 33.33

Performance Mode: Standard

DRAM Timing Selectable: Manual

SDRAM CAS Latency: 4T

SDRAM RAS to CAS Delay (tRCD): 4T

SDRAM Row Precharge (tRP): 4T

SDRAM Active to Precharge Delay (tRAS): 12T

SDRAM Write Recovery Time: 5

Write to Precharge Delay: 15 (If it's Listed)

Command Rate: 2T

DDR2 SDRAM Voltage: 2.1

CPU Core Voltage: Auto

FSB Termination V: 1.50 V

MCH Chipset V: 1.65V

ICH Chipset V: 1.20V

All other settings are motherboard defaults.


I bumped up the RAM voltage to 2.1v, and although the terminator voltage option he recommended was 1.5v, my BIOS maxed at 1.45, so I used that.


The system booted and was stable. But it offered no real speed advantage in a video benchmark test. I do alot of video, hence my attraction to the quad. Most video apps are Multicore aware.


I kicked in Asus Ai-NOS with a 10% boost, and the system became unstable. It wouldn't even boot.


Ai-NOS is supposed to only bump up the clock under load, yet it wasn't even booting for me. It worked fine when I went back to the Auto memory settings, and left Ai-NOS enabled, with 15% boost. It also gave a 17% speed improvement in the same video benchmark, set at 15% boost.


Why didn't the RAM settings work with NOS, and why did it offer almost no speed advantage when NOS was turned off?


I'm a noob OC-er, so I suspect I'm missing something obvious here.

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I never use software to overclock my system. It just does not work correctly for me. Keep in mind that you can not specify your ram settings and then attempt to allow NOS to overclock. You must set all to Auto to allow the NOS to make changes. The system will gauge the timings necessary at an overclock level and this also includes the DRAM. You are telling the system to take over but then you are controlling the settings.


Is your board the P5V? Not the P5B-E or P5B-Deluxe? If so, you have the vanilla board which is not really set for overclocking and does not allow you to make the kinds of adjustments necessary for good stable overclocks.


It is always necessary to research the board very well if overclocking is your choice. That board is NOT overclocking friendly. The P5B-Deluxe is though.

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