I think the BH6 is based on the Intel BX chipset, so it is not supposed to officially support 133 MHz FSB. There is a setting for it, but that is considered overclocking and as JackMDS said it doesn't have a divider for the AGP slot so you are overclocking the video card too and a lot of video cards (especially older ones) can't take that. If you are looking to upgrade, I would suggest maybe a PIII with a 100 MHz FSB so that you can have it at regular core clock and still have good performance or you can overclock it if you want. That's what I did. Originally I had a PII 350 MHz in my machine and I upgraded it to a PIII 850 MHz.