Thank you all

Actually tanuki got 5.827GHz with his 631 under air cooling:
Temp: -4C at his veranda





So far 5.955GHz is the highest clockspeed under LN2: By Cal930
He believes he can get much higher from this chip but suspects his M/B sucks

CPU（Lot No.）：Pentium4 631（SL94Y L546B029 MALAY）
Cooling：KuriPro4 LN2
Vcore(V)：1.821v
M/B：ASUS P5WD2-E Premium Fully Vmod
VGA:X1900XTX(Driver from CD)
Memory：CORSAIR PC2-5400C4 512MBx2
Vddr(V)：2.55V
FSB/RAM Ratio：4:5
DRAM Timing：4-2-3-4-2-D-D(bios)
OS：WinXpProSP1