We benched the same board up to -160 the day before at 6400Mhz with another CPU. IMC was crap of that 2nd CPU. Max bootable was just below -100°C with 2600mhz ram speed... but barely stable, just a 32M... then she would go out if we stressed all cores...
The 3770K one we did today had major cold issues at -120. Also couldn't boot with temps lower than -100°C with RAM clocks of 2600Mhz. 2800Mhz was no go, no matter the temps. 3750K was so sweet at 6.3 with 2800Mhz RAM...