I have a Computer In the Car, I use the EPIA 12000
this is a link, http://www.cardomain.com/memberpage/722913
I have found that a software called SpeedFan had control over my EPIA 12000 FSB, Speedfan also has other cool functions.
I can control Overclocking amount based on CPU Workload.
If Cpu Above 60% then It will ran at Overclocked Speed.
If Cpu is Lower than 60% I have the CPU to be underclocked.
It also shows Tempature in the System Tray.
Best is to download and install it, then experiment with settings, I have got upto 150MHz from the FSB and is stable.
This is the Link: