I have never used AMD 64 processors, but I suppose Cpu Frequency Scaling should work on it like on any other CPU.
Make sure you have kernel support for CFS enabled. Note that 2.4 kernels do not include support for it.
find /lib/modules/yourkernelversion -name "cpufreq_userspace.ko"
If this module is found, then all should be ok. Next make sure you have appropriate CFS daemon installed. I prefer "powernowd", because it is the simplest. There are others which you can try, for example "cpudynd" and "cpufreqd", but they are not as simple.
Also check you BIOS settings. Some laptops have defaults options for the CPU frequency. Even if you can't make real Linux CFS to work, you might be able to set the default to 2.2Ghz from BIOS. When you need long battery life, you could switch that default to 800Mhz temporarily.