ok, that is a 400MHz bus Celeron. What I meant, that in some cases the CPU can be overclocked, as to run at 533 MHz bus. There a guides around this subject on the web.
Look at ECSs site for the motherboards equivalent model and see its CPU support list, should be almost equal to your board.
Syntax disappeared long ago, however, there was a webpage or ftp site up, with all the Syntax BIOSes and Manuals collected, not too long ago. Can't remember its name though. You could also try the Wayback machine if it finds something.