Still no speed bus

I've typed the code in openfirmware to overclock the bus speed like 15 times and it still doesn't work! Does anyone have any advice or alternate code to use? I swear, I can't be that stupid. I tried the magic code into the openfirmware of my Dual 500mhz Gigabit multiple times but it made no difference on each restart. The system profiler still reads 100mhz and nothing changes. I even tried the code to overclock it to 167mhz. I think the issue might be the particular models I have. I wonder if certain revisions were able to do it and others not. Or maybe I'm just not that good at typing in code.