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Problem using all 4 slots


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**Sorry, posted in wrong forum originally**


In my personal system I ran into an issue when filling all 4 DIMM slots (4x1GB). The system would be unstable, it would hang on boot, etc. I took one stick out and haven't thought much about it since.


Today however I received parts to build a PC for a family member, and I'm having the same problem. These are the parts:


Asus P5Q Pro Turbo motherboard

Intel Core 2 Duo E7500

4x2GB DDR2 800 (Corsair XMS2 CM2X2048-6400C5)

BFG GeForce GTX 260 896MB PCI-e

Corsair CMPSU-750TX 750W

Western Digital Caviar Green WD5000AADS 500GB SATA drive

SAMSUNG DVD Burner Black SATA Model SH-S223L

Windows 7 Home Premium 64-bit


During Windows setup the installation froze several times. After removing one pair of memory modules everything has been fine. It doesn't matter which pair I have in, it works fine with just the one pair. If I add the second pair however, windows never boots. Sometimes it hangs on post, normally it will hang on the "Starting Windows" screen.


Clearly there's something I'm missing. This is the exact same problem I have with my personal machine (EVGA 680i SLI motherboard). On mine I just chalked it up to a flakey memory slot or something with the motherboard (I tried replacing the memory but the new pair did the same thing). What is it that I'm missing here? Pretty much the only thing these machines have in common is me building them and both are Corsair XMS2 (mine are CM2X1024-6400C4).


I posted on a forum elsewhere and was told "It happens all the time. Are you sure the memory sets it's speed and latency correctly when you put all four sticks in? If not, check to see if your board has the latest BIOS version on it." I know on my personal machine I have the latest BIOS version, I haven't checked this new build yet. As far as manually entering information, I'm unsure what is safe and what is not. The Corsair support site lists the following, which I figure is my issue:


Troubleshooting Tips for DDR2-800 (XMS2-6400C5)


Tested Settings for this Module: Speed: 800MHz Latency: 5-5-5-18-2T Voltage: 1.8



Here are some common tips that you should try before proceeding with a full technical support case.


Four modules won't run at the speed and/or timings I expect them to.

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If both pairs work individually you are running into a limitation of the motherboards/northbridge's memory controller. The timings and speeds are only rated for two sticks unless the quad kit was purchased. There for you will most likely need to slow the memory down to 667MHz in order to let the memory controller run all 4 modules without any errors.
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