Question Overclocking memory on an old 2500K, Update found the magic setting

[CU]

Swapped my 8Gig kit for a nice 16Gig Team Xtreem 2666 C11 1.65v as I needed more then 8Gig. Figured I should be able to hit 2133 or at least 1866 as a bonus. Problem is I can only do 1600. Now I can do it at 8-8-8-24 1T with all volts set to auto and Dram volts at 1.65. But, 1866 and up just causes it not to post a few times then it boots at 1333. I have tried 1866 at 14-13-13-35 2T with VCCSA at 1.105, VCCIO at 1.25, and Dram volts at 1.7 without any success. The CPU is not overclocked at all with everything set to auto / default for these tests. Is there anything I am missing, or am I just out of look. I guess 1600 C8 is OK. Just expected more from them as I couldn't find any case where someone couldn't run a Sandy Bridge above 1600. So, if anyone remembers any secrets to overclocking ram on an old Sandy Bridge let me know.

 

[DrMrLordX]

Careful with the vDIMM. Some of those Intel IMCs can be sensitive. I remember it being an issue with Nehalem . . . not sure if Sandy was the same way.

 

[CU]

I just tried 1.7 once to see if it made any difference. I wasn't going to leave it there. 1.65 should be safe for Sandy and that is what a lot of the higher rate ram is suppose to run at.

 

[DrMrLordX]

This is all I found:

Why is 1.65V memory bad for Sandy Bridge Processors?

I just now read that Sandy Bridge processors are supposed to work with 1.5V memory instead of 1.65V memory in the Sandy Bridge thread. The tolerances are supposed to be +-5%, which 1.65V memory definitely doesn't fall into. What exactly could happen by running my memory at 1.65V instead of 1.5V?

forums.tomshardware.com

1.65v is about the limit. There's more to it than that, but essentially those memory controllers can be touchy.

 

[CU]

I think I found the magic setting. I ran Thaiphone Burner and noticed that the tRFC for the 2666 XMP profile was 400. My MB was setting it to 144 when I selected the XMP profile. It also maxes out at 255. That's probably why it doesn't read 400 correctly. So, I set it to 255 and set the speed to 2133. It made it to windows, but google's stressapptest would error. So, I added a little voltage to VCCSA and VCCIO setting them to 0.955V and 1.100V respectively. That made it stable in stressapptest. Then I tightened the timings down from the 2666 XMP settings to 9-12-12, and it still passes 1 hour of stressapptest. So, it seems the tRFC was the magic setting that made it go from not even posting at 1866 to getting into windows at 2133. And, now I have 16gigs running at 2133 C9.

I know DDR3 overclocking on Sandy Bridge is old news now, but maybe it will help someone. As I couldn't find any guide that mentioned raising tRFC.

Now to decide if I want to sale my 2500k and get a 2600K. 3770K would be nice, but not worth the price over the 2600K.