12 GB CMX6GX3M3A1600C9 suddenly 10 GB

[JcRabbit]

Ok, this was very weird:

 

System has been running stable for months. Yesterday I upgraded from 6 GB of RAM from another manufacturer to 12 GB Corsair DDR3 1600 Mhz RAM, in two kits of three.

 

I installed the 12 GB of Corsair RAM, set the XMP profile in the BIOS, reset the CPU clock multipliers for the previous 4 Ghz CPU overclock. The 12 GB of RAM were properly detected on first boot, Windows 7 detected 12 GB, and everything was going smoothly.

 

After roughly 24 hours running without any problems, Windows suddenly Blue screens with a memory error.

 

After that, no matter what voltages I changed in the BIOS, only 10 GB of RAM were being detected, both on boot and by Windows. CPUZ could still see 12 GB. Setting RAM speed down from 1600 Mhz to 1200 Mhz didn't fix it either! I tested those 10 GB with the Windows Memory Diagnostic tool, no problems.

 

So I removed three of the memory sticks to test each set of three individually.

 

Now, when I did that, turned on the PSU and hit the power switch, the board turned on, turned off, and then on again. I have seen this on a previous Asus board, with Asus saying it was normal for the board to reset something I can't remember what it was now, sorry.

 

I tested the first three sticks with the WMD, no problems. Swapped those three sticks with the other set, tested, no problems. So the RAM itself seems to be ok.

 

Now (and I suspected this was going to happen after that board reset) when I inserted all 6 memory sticks and rebooted, all 12 GB were again properly detected, and passed the WMD with flying colors.

 

My question is: anybody has any clue of what happened here? Why weren't the 12 GB being detected properly after the failure, even at 1200 Mhz, until I removed the RAM to test it in groups of three?

 

I've now left QPI voltage on Auto in the BIOS (instead of the 1.2v set by the XMP profile) which TurboV reports as 1.375v, but I'm afraid to get another blue screen and again having to go through the trouble of removing three sticks of RAM, rebooting, and putting the three sticks of RAM back in.

[Synthohol]

it could be due to one or more of the following.

 

bent CPU socket pin

CPU pin making poor contact and pressure on the board while exchanging ram sticks

poor contact or bent RAM socket pins

BIOS issue

mixing 2 ram kits that were not tested on a single board

different versions of ram kits

weak or failing memory controller on the CPU

not enough QPI volts i believe 1.4 is suggested when using 6 sticks

bad mojo.

 

the thing is...mixing 2 separate kits is never suggested or recommended, you always have a better chance successfully running 6 sticks if they ALL were sold as a SINGLE 12Gb kit.

 

please read this Corsair document. http://forum.corsair.com/forums/attachment.php?attachmentid=6937&stc=1&d=1275030547

 

good luck!!

[JcRabbit]

mixing 2 ram kits that were not tested on a single board

different versions of ram kits

...

the thing is...mixing 2 separate kits is never suggested or recommended, you always have a better chance successfully running 6 sticks if they ALL were sold as a SINGLE 12Gb kit.

 

Thanks Synthohol!

 

I had no choice but two use two kits, single 12 GB kits were not available. On the other hand, the two kits used were sequencially numbered, i.e.; same lote and all, only difference is that one says 'Qt 3/24' and the other 'Qt 4/24'.

 

In the mean time, with QPI on Auto, so far so good (fingers crossed).

 

What really surprised me at the time was that even setting RAM speed to 1200 Mhz did not cure the problem - I'm pretty sure nothing I could have possibly changed in the BIOS would have made a difference until I tested each kit separately.

 

Lets hope it was a pin contact problem and that reseating the RAM fixed it for good.

[trackrat]

In addition to the possibilities Synthohol listed there is a known issue with X58 chipset mobos and disappearing memory.

 

http://forum.corsair.com/forums/showthread.php?t=82274

[Wired]

X58 and P55/H55/H57 Platforms actually.