See the Asus P5K overclocking thread. Has tones of details
The fsb strap should be 333 and you will need to up the CPU Vcore to get stability at > 3.4. Depending on your VID (found within coretemp), you will need about 1.3 volts for 3.4 although it is important to remember that all chips are different. Once you have stability (use Prime - small ffts to test this), lower the vid until it is just stable.
It is also wise to drop the timmings on your ram whilst overclocking - to say 7-7-7-20 as this helps to eliminate ram related problems when testing for stability.
Here are some reference settings for you for a 3.8Ghz clock:
multipler 9
Strap 333
FSB 425
Pcie 100
Dram 851
Command rate 2n
Ram 4/4/4/12/4/25 everything else auto
Dram SRC auto
Transaction booster level 0
V Core 1.525v
PLL 1.5v
FSB TV 1.30v
NB 1.40v
SB 1.05v
Cpu spread spectrum disabled
Pci-e spread spectrum disabled
Clock over charge auto
Load line calibration enabled
CPU GTL auto
NB GTL auto
Here are some reference settings for my Q6600 when i had it clocked (Mobo was a P5K Premium) - hope this helps.
