Asrock K7VT2 motherboard problem

Question

Swapped motherboards in a PC at home going from an Abit KT7A to a Asrock K7VT2 using the same 1200Mhz Thunderbird.  When firing up the bios would only recognise the processor as a 900Mhz CPU.  The FSB was set at 100Mhz as it was on the KT7A (x12) but the Asrock wouldn't allow me to achieve this in the bios.  The only way I was able to get it recognised was by manually setting it up in the bios as having an FSB of 133Mhz with same clock multiplier of 9. Is this correct?  Or should I be able to run it as 12x100Mhz as I did with my Abit motherboard. Any ideas?