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

CU

Platinum Member
Aug 14, 2000
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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

Lifer
Apr 27, 2000
15,406
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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

Platinum Member
Aug 14, 2000
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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

Lifer
Apr 27, 2000
15,406
4,158
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This is all I found:


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

CU

Platinum Member
Aug 14, 2000
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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.
 
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