p3 667's have multipier of 5 and a fsb of 133, PC100 is rated for fsb of 100 but sometimes can do 133 or even exceed 133, based on whether it's CAS2 or CAS3 and what it's running at. Therefore, it is possible for the PC100 RAM to run at 133... although it should be 133 hope I answered your question... anyothers, just post 🙂