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CORSAIR XMS2 DHX & Asus P5n72-T Problems?


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I have 4x CORSAIR XMS2 DHX 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop on an Asus P5n72-T Premium MB. BFG 9800 GX 2, Vista 64.

Here are the facts:

-Memory passes MemTest86+ 2.01 7 passes, zero errors at 4-4-4-12-T2 2.1v, as well as 4 passes zero errors on what ever the BIOS sets as defaults.

-In Vista, system is horribly unstable. At least one lock up per 15 minutes...usually within 10 minutes.:(:

-I have tried both latest vidio driver and 2nd most recent.

-All chipset drivers are current

-All temps within specs...CPU (Zalman cooler) Idle=9c Stress=17c

-CPUZ reports: DRAM FREQ 400 FSB:DRAM 5:6 CL 4.0 tRCD 4 tRP 4 tRAS 12 tRC 23 CR 2T


Does this memory work with my MB? If so, what settings do you suggust? That it passes with flying colors memtest...yet fails so horribly in Vista makes me think Memory is ok...but, I dont know for sure.


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The reason Memtest passes and the system is unstable is because your on motherboard memory controller (MCH) is not liking the setting of a four DRAM slot population as fast as a two DRAM slot kit can run. Insert just two sticks. Enter your BIOS. Lower your DRAM speed from 800 to 667MHz. and increase your MCH/Northbridge voltage to 1.45v.

Download memtest from--->

and extract the ISO image. Burn the ISO image to an CD-ROM disk.

Download CPU-z from-->

Please research this thread:




The issue is the memory controller and a population of all four banks at the full speed of a two bank run. This issue is across the board with both Nvidia and Intel chipset based boards, DDR, DDR2 and DDR3.


Keep in mind that often issues arise in the longer term. The issues seldom damage the DRAM. They damage the on motherboard memory controller which has a harder time keeping up with the demands of a four DRAM slot population being run as fast as a two DRAM slot population. Those who want to be secure in their system either purchase a single kit of the DRAM capacity that the four singles have or they move to a higher bandwidth DRAM and drop the bandwidth. I also advise it as I have personally seen the issues that can and often do arise with a four DRAM slot population running at the full speed of a single kit speed.


I personally advise for a two stick solution as it is far gentler to the motherboard memory controller.


Boot to the Memtest CD and allow for two full passes. If you pass, then enter Windows, run CPU-z and post your CPU-z CPU, Memory and SPD tabs.

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I will try your suggustion shorty. first, and update...

I saw a post on another forum from someone with exact same MB/Memory problem and he said the only way he could run his stable was to OC it. Shure enough, when I set my Ausus AI Suite to OC to 10%...it has yet to crash even with all the torture test I throw at it.

Current CPU-Z results with the 10% OC:

DRAM Freq = 420.3


CL = 5.0 clocks

tRCD = 6 clocks

tRP = 6 clocks

tRAS = 19 clocks

tRC = 24 Clocks

CR = 2T

So...Would I still be better lowering the speed to 667? I hate to have to drop to 4gig, but if that is the only way I can safely use this MB...may have to. Wish Asus would not advertice 8gig / 800Mhz...seems misleading.

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With 4 modules I would suggest setting the memory frequency at DDR667 and set the memory Voltage to 2.1 Volts and set the NB/MCH/SPP Voltage to +.2 Volts as well and test the system with http://www.memtest.org. In addition, with some MB's (Mostly ASUS) you have to disable legacy USB in the bios when running any memory test.
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