So I have the xeon listed in the title and I've had a hard time overclocking with this chip. At 1.3V I've hit 4 ghz and 4.1 is unstable. Upping the voltage to 1.35v It won't even boot at 4.2ghz. Raising other voltages listed in guides really increases vreg Temps too. It hit as high a 95 degrees. Must mod a fan or something. This board is giving me a lot of grief

Everything is on auto except the cpu vcore which is at 1.3v and the cpu vtt is +100. I've seen many guides show the other settings at 1.4v but that seems like one hell of a leap.

Are you meaning hardware?

Evga x58 3 way sli revision 1.2
Xeon x5680
Corsair Vengeance CMZ12GX3M3A1600C9 12GB rated at 1.5v
H80i
Nvidia 970

I'm not sure on the bios but this board was just rmad.

Give these settings a try.
 
Frequency Control 
CPU Clock Ratio ( 25X )                                                                                          
CPU Host Frequency (Mhz) ( 168 )                                                                       
MCH Strap ( Auto ) 
CPU Uncore Frequency (Mhz) ( 2688Mhz { 16X } )                                                 
CPU Clock Skew ( 0 ps ) 
Spread Spectrum ( Disabled ) 
PCIE Frequency (Mhz) ( 100 )

Memory Feature         
Memory Speed ( Standard ) 
Memory Control Setting ( Enabled ) 
Memory Frequency ( 1680Mhz / 2:10 )
Channel Interleave Setting ( 6 Way ) 
Rank Interleave Setting ( 4 Way ) 
Memory Low Gap ( Auto ) 
tCL Setting ( 9 ) 
tRCD Setting ( 9 ) 
tRP Setting ( 9 ) 
tRAS Setting ( 24 ) 
tRFC Setting ( 128 ) 
Command Rate ( 2T ) 


Voltage Control 
EVGA VDroop Control ( Without VDroop ) 
CPU VCore ( 1.35 )                                                                                                 
CPU VTT Voltage ( +50 ) 
CPU PLL VCore ( 1.80 )   
DIMM Voltage ( 1.50 )
DIMM DQ Vref ( +0mV ) 
QPI PLL VCore ( Auto ) 
IOH VCore ( Auto ) 
IOH/ICH I/O Voltage ( Auto )  
ICH VCore ( Auto ) 


CPU Feature 
Intel SpeedStep ( Disabled ) 
Turbo Mode Function ( Enabled ) 
CxE Function ( Disabled ) 
Execute Disable Bit ( Disabled ) 
Virtualization Technology ( Disabled ) 
Intel HT Technology ( Enabled ) 
Active Processor Cores ( All ) 
QPI Control Settings ( Enabled ) 
QPI Link Fast Mode ( Enabled ) 
QPI Frequency Selection ( Auto ) 
OC Recovery ( Disabled ) 
Turbo Performance ( Disabled )
 

If you have the option to set your CPU Impedance to "Less", and the QPI Compensation to "Less" give it a try.  That helped my 4.4GHz overclock. 
 
It is said when the Core speed reaches ~ 4.5GHz it has an effect on the QPI bus, even if the QPI bus is below stock speeds.  I would use set the CPU Impedance to "Less" to start off with. 
 
Also keep an eye on the QPI speed.  if it's above 3.2GHz then you might need to raise your IOH vcore, and QPI PLL.  Keep these volts the same.  I keep my volts between 1.2 - 1.3v when the QPI bus is high. 
 
If your Uncore is around 3GHz 1.2-1.275v CPU VTT is sufficient. 
 
4Ghz is an easy overclock for these Xeons.  If you can't dial in the board then it might have been an abused chip. 

@bill1024 i have exactly the same combination as you, evga ftw3 + x5660 but i have no chance to get my xeon near to 3.8 Ghz
 
Please can you give your bios settings? that would be great!

bill1024
If those settings do not help, this is my settings
 
I have the FTW3 with x5660, I find with the xeons the uncore needs to be 2 times ram speed or one click lower.
This seems to be true on both my FTW3, my Rampage3, and my Asus P6T V2 D boards.
Keep the CPU and VTT  at or under 1.35v
 
For some reason I have better stability with odd number multi for the CPU  21 23 25.....
 
I run 175x 23 the CPU at 1.3v and +150 on the VTT  or 21 x 200
The newer boards the VTT is 1.2v base so +150mv is 1.35v  classified and FTW........
The older boards the VTT base is 1.1v so +150 should be 1.25
 
Try running the ram at 14xx for now with 9-9-9-25 timings Raise the ram voltage to 1.6v uncore 28xx
If that is stable raise the BCLK a few points at a time and see.
Raise the CPU and VTT a little at a time to get stable keeping under 1.35v and uncore at 2 x ram speed.
 
Then work on your ram, I find over 1600 is no great gains anyway, can try for tighter timings. 7-7-7-21 --1
My 1600 ram is at 14xx and my 1866 runs around 1820 -ish
 

Old thread, but I wanted to thank you for the information here!  I've been looking everywhere for exactly this sort of template, believing my RAM was causing my system's environment to become unstable with what felt like a really low OC for the 5660 processor.  I had no idea how uncore worked (or what it really did) and this has helped a lot. (Especially the templates ya'll drew up.)  I've gone with the x2 rule - I'm able to run my 5660 at around 3.8ghz with my RAM at near 1333.  (Pushing the BCLK any higher pushes the RAM above 1333. I'm worried this RAM doesn't OC very well. I could very well be wrong, now that I'm putting the correct uncore values in.)  Feels stable, so far, with my voltage at 1.25 and VTT +100mv and other settings 'stock.'  Not too shabby for a $50 six-core upgrade!   I wish I had 1600 rated RAM (assuming this is what's holding it back from stability under load), so I could possibly push this OC to 4.0, but not sure it worth the extreme prices (or degradation of the already used chip) - maybe something used on eBay, etc.   Thanks again!
 
Note:  If anyone is having trouble with RAM not being recognized properly, don't use the XMP profile.  Just does not work with 12GB in Tri-channel, for some reason.