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HOW TO: Getting two kits of 16gb ram stable on a Sabertooth X79

Last response: in Motherboards
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October 4, 2012 6:12:44 AM

I couldn't find this specifically posted anywhere, so I thought I would post it up here. For the last few weeks I have been battling to get two 16gb kits (4x4gb) and (4x4gb) two work together and be stable on my mobo. I looked all over the net and I couldn't find anything that specifically fit my situation, so I thought I would post how I got it stable in hopes that it will help someone else down the road.

Big thanks goes to jaquith. Without his base work that I gleaned from other threads he replied to, I would have never been able to get this done.

My Setup:
Motherboard: Asus TUF series Sabertooth X79
RAM: Corsair Dominator GT 2133MHz 16gb kit x2 (CMT16GX3M4X2133C9)
RAM Profile: XMP
Processor: i7-3960X

**Because XMP automatically overclocked my processor from 3.3GHz to 3.9GHz, I had to raise my Vcore slightly to get the overclock stable.

What I Did:
In order to get the ram to make 5 passes of memtest86+ with no errors, I had to adjust some voltages, the CAS timings and the PLL. It should be noted that some of these settings could probably be dialed down a bit, but I don't have time to incrementally test that.

Voltages:
Raise DRAM bank voltages from 1.5v to 1.55v
Raise VCCSA voltage up to 1.2V
Raise VTT voltage up to 1.2V
Raise PLL to 2V

CAS Timings
Adjust CAS timings to 10 10 10 30 2N

After doing these things, I was able to get 5 passes with memtest, having all 8 DIMM slots populated with both kits. AIDA64 stress test also runs buttery smooth with no errors.

If you have a similar setup to mine or then identical one, I hope this helps you out.
a b Ĉ ASUS
a c 180 V Motherboard
October 4, 2012 6:12:41 PM

It also helps to not fill all the ram slots and to have used 4x8gb, this helps the motherboard to be able to address the ram sticks better.
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October 4, 2012 11:26:48 PM

True, but where I am located in the world, a kit like that is hard to find. So, the best I could get out of the vendor I used was two kits of 16gb that populated all the DIMM slots. The point of this how to was to help any other lost souls that wound up in my situation. I would rather someone stumble across my post and solve their problem in 5 minutes than the over the week it took me.
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a c 207 Ĉ ASUS
a c 717 V Motherboard
October 4, 2012 11:56:32 PM

Now, you 'might' be able to lower the CAS Timings a bit if you're willing to raise the DRAM AB/CD Voltage higher and by higher I mean 1.60v~1.70v and lower the PLL down to 1.85v~1.90v.

I run 8xDIMM and it's the frequency that's the issue and obviously you need to contend with keeping all of the DIMM's properly powered.

Additional, tweaks for RAM when OC'ing the CPU also help:

VCCSA Load-Line Calibration -> Regular
VCCSA Current Capability -> 120%

DRAM AB Current Capability -> 120%
DRAM AB Power Phase Control -> Optimized
DRAM CD Current Capability -> 120%
DRAM CD Power Phase Control -> Optimized
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October 5, 2012 12:01:54 AM

Unless I've set something that is going to cause my computer to go boom, I'm quite happy with getting it stable. I've been fighting with this issues for weeks and the only reason why I was able to solve it is that I'm on a week's national holiday right now. This is my main computer and I don't have much time for it to be down for maintenance and tweaks.
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a c 207 Ĉ ASUS
a c 717 V Motherboard
October 5, 2012 1:27:12 PM

I provided additional options IF you want to gain access to lower CAS @ DDR3-1866 with those kits.
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