CPUcb or NBcb? for NBcb try pcieclk 107/112.Many cpu with NBcb near -150/-160C go to full pot.

ratio 3:10 you have cold boot problems with 1:4, i guess imc/Nb is the problem

Tbh I didn't know NB had CB. Figured it was just CPU. Will try again with some PCIe CLK, see if it helps. Was quite low, was getting CB at about -90c

Tried again on the Asus board. -90c and CB. Tried increasing PCIclk and running 1:4, made no diff unfortunately :(