You have cool and quiet enabled in the bios, that reading of 800Mhz is cool and quiet lowering the the core frequency of the cpu, As soon as you run an intensive program the clock speed rams up to the max the cpu can operate at and auto change the multiplier.
The other is the Fsb of the cpu is 200Mhz, so set that then you want a multiplyer of 17. 200x17=3400Mhz.
The stock speed of the BE. Next you need to set the right revision of silicone the cpu is using the stepping. And set the frequency Cpu DID to the right setting it wants.