Help setting GTL refs please

[thomas hobbes]

Been messing with my new QX9650 picked up 2nd hand and its proving a thirsty overclocker. I need to put 1.45v through the CPU core for an overclock of just 4GHz (400 x 10) and 1.47v on the FSB. My motherboard is fully water cooled so I'm not unduly worried about these high voltages in the short term.

Ive read up on how to calculate GTL's here (http://www.xtremesystems.org/forums/showthread.php?t=202292) and have followed the formula (Vtt x 0.667 + Y = Vtt x 0.635) to get an accurate GTL figure of -50 mv. So far so good.

My question is this, given that my motherboard allows me to set four GTL refs independently do I need to set them all to -50 mv? I currently have GTL 0 & 2 set to -50 mv and GTL 1 & 3 on Auto and its been stable for almost 3 hours. But setting all four GTLs to -50 mv gives instability.

Why is this?

[CryptiK]

I'm not familiar with your board, but I would assume that you have 4 GTL Ref settings each with a fixed ratio of either 0.635x or 0.667x. You don't need to set them all to -50mv, as a starting point just set the the 0.667x ratio GTL Refs to -50mv, making them produce the same Vref that the 0.635x ratio GTL Vrefs do when they are left on auto. Then again you could always leave the 0.667x GTL Refs on auto and set the 0.635x GTL Refs to +50mv. Just play around with them to see what gives the most stability, the guide just explains where to start from, and how to calculate the right values, finding what your particular setup likes is up to you and will take some time and patience.

[thomas hobbes]

I'm not familiar with your board, but I would assume that you have 4 GTL Ref settings each with a fixed ratio of either 0.635x or 0.667x. You don't need to set them all to -50mv, as a starting point just set the the 0.667x ratio GTL Refs to -50mv, making them produce the same Vref that the 0.635x ratio GTL Vrefs do when they are left on auto. Then again you could always leave the 0.667x GTL Refs on auto and set the 0.635x GTL Refs to +50mv. Just play around with them to see what gives the most stability, the guide just explains where to start from, and how to calculate the right values, finding what your particular setup likes is up to you and will take some time and patience.

Thanks, but how do I know which of the four GTL refs are 0.667 ratios and which of them are 0.635x ratios?

My 790i FTW board displays the MVs as absolute values not ratios. Hope that makes sense.

[Anth Seebel]

OK try these..

OPtion 1:

-50mv
-50mv
-20mv
-20mv

Option 2 :

-30mv
-30mv
-10mv
-10mv

Option 3: (worked best for my QX9650 ES/790i Ultra)

-15mv
-15mv
00mv
00mv

OPtion 4:

+15mv
+15mv
+25mv
+25mv

See what option is most stable and then find out which core is failing first via P95 small fft's.. then adjust accordingly.. GTL ref takes alot of testing but the results can make all the difference to higher stable clocks.. :up:

[thomas hobbes]

Thanks I'll give these a go...