My Thunderbird 800 is currently running at 884Mhz. I think I put the multipler up to 8.5x and the other thing (FSB?) to 103 or something like that. I did get it to over 930Mhz (935 or something) but I chickened out of running it that fast and reverted to 884Mhz. I haven't had a single crash or anything, so I'd recommend you have a go. (It helps if your mobo is rock solid like my K7T Pro2 (three weeks and no crashes!)).