CMZ16GX3M4X1866C9R and Asus P9X79

[McThrustin]

I have just bought a new rig and it seems I'm having the rather common issue of having the wrong amount of memory detected when attempting to run the memory at its listed speed. I've tried a bunch of stuff but it seems I may have to tweak the memory settings a bit more than I'm familiar with (I'm used to the 9-9-9-24 2T type thing but not much more.)

Using the built in XMP profile the system is stable but only 12GB are detected. Downclocking the system to 1333MHz makes all DIMMS detect properly. I have confirmed it's not a memory issue as the DIMMS work individually or in pairs at the advertised speeds but once I get to 4 one will show up in the BIOS as 'Abnormal'. I have also returned one set to the store and exchanged for a new one, but the same issue is arising so I'm almost certain it is not faulty RAM or the Motherboard.

Your memory finder tool lists the ram as compatible with the settings (7-8-7-20 2T @ 1.5 volts). These settings will stop my machine from even posting at speeds over 1333MHz.
At this point I'd be happy with even getting it to detect all 4 at 1600MHz.
You can see the memory finder results here.

Anyway, here's my system details:

Intel Core i7-3820 @ 3.60GHz
Asus P9X79 with lastest Bios (1103 x64)
Corsair Vengeance 16GB Quad Channel Kit (CMZ16GX3M4X1866C9R)
Corsair AX650 PSU

Any help or advice would be appreciated.

[peanutz94]

You could try adding memory controller voltage. You can either look through you manual or contact ASUS to be sure which one it is. That same setting is called a few different things depending on board and BIOS. I have seen everything from VTT, VCCIO,QPI and so on.

I do know 1.05v is stock and you can go to a max of 1.4v (absolute max) But i wouldn't go over 1.25v to be safe.

Here is a good guide to SB-E definitions although it is a gigabyte board. Most of them should be the same or close to it.
http://www.overclock.net/t/1189242/s...9-overclockers

[McThrustin]

I seem to be having a hard time finding out which setting specifically adjusts the Memory Controller Voltage. I have checked online and in the manual.

I suspect the setting is VCCSA, which the XMP Profile is setting already to 1.2. Adjusting it to 1.25 has done nothing.

Other settings that may be the controller:

VTT CPU
VTT DDR (2 settings, one for each memory pair).

One other question, do you recommend I test with the XMP settings or the ones listed on your memory compatibility checker (The ones on your checker are quite fast)?

[RAM GUY]

Go to BIOS setup and load setup defaults then exit saving changes and let it boot to www.memtest.org disk. Thew restart and go back to BIOS and enable XMP and check the Voltages you should see a slight increase on the memory controller voltage with XMP enabled.

[McThrustin]

Well,

After playing around with the DIMMS it appears that one in particular is causing problems if it is seated in the machine with more than 1 stick of ram. I will run some memtests on it. It could be just bad luck that I got 2 packages with a bad DIMM. I'll let you know.

[McThrustin]

After going to the retailer and testing out 2 more quad kits that have been confirmed to work on other machines, the same problem has arisen. It looks like it's a bad Motherboard and the Ram was just fine. Thanks for your help though!

[RAM GUY]

NP but glad it seems you have the issue narrowed down, please let us know how you make out.

[Turbonerfs101e]

hi your timing issue is normal
((Your memory finder tool lists the ram as compatible with the settings (7-8-7-20 2T @ 1.5 volts). These settings will stop my machine from even posting at speeds over 1333MHz.))
If you run memory at a slower speed you could run it at a lower latency
So your CMZ16GX3M4X1866C9R set at 1333MHz 7-8-7-20 T2
You could even do 1600MHz 8-9-8-24 T2
Or you 1866MHz 9-9-9-24 T2 it maximum tested speed
Hope this help
Sincerly yours

[peanutz94]

Turbo, he solved this. It was a bad MB

After going to the retailer and testing out 2 more quad kits that have been confirmed to work on other machines, the same problem has arisen. It looks like it's a bad Motherboard and the Ram was just fine.