600B is a Coppermine CPU. 600B runs at 100mhz FSB. 600EB would be the 133mhz FSB. I know, because I have one. Mine runs at 800mhz, no problem. May go faster, but I have never tried. You will need high quality RAM to do 800, most likely. I could not get 800 until I bought some Mosel Vitelic Rev.2 CAS 143.