Cpu and fsb

Hello i aw new here i was reading loads of forums about fsbram ratio...My Mb is asus p5ql-em ,Cpu 8400 3.ghz (333x9) and dram is Patriot ddr2-800. I was trying to do fsbram ratio by setting the ddram to 667 and set my cpu multiplier to 7.5 and maked fsb till 400 ...in the end of this the cpu was still 3ghz and ddram was 800mhz because then was rising fsb aswell ddram rised from 667 to 800 so 400:400 ratio...the problem was that my bios gived me a fault ..was written overclocking failed or overvoltage... whats can it be wrong ? is there any difrent ways by my config to do ratio 1:1 ?