The Toshiba Tecra 8000 motherboard that was supplied in the original system build has been specifically configured for the supplied processor. Substituting the processor with different model is fraught with a number of problems including CPU electrical differences and motherboard BIOS (CPU microcode) support incompatibilities.
Typically insertion of a miss matching CPU will result in the system's failure to boot, and abnormal behavior (which is consistent with your observations).
As far as I am aware there are no jumpers on the motherboard that may be reset by hand, and I am not aware of any alternative BIOS images that you could try.
Generally there is little in the way of information on the www about overclocking this model of laptop.