Saving power in xen

My setup:

AMD Athlon 5050e (dual core energy efficient)
8GB Ram 1.6V
2 Disks Hitachi HDT721010 mirrored

OpenSuse 11.1

Goals:

• Server for running a brunch of virtual machines
• energy efficient

To lower the energy costs i wanted to reduce the number of running machines. So i read this:
http://wiki.xensource.com/xenwiki/xenpm
At the time i read this, all sounded very good, but i learned that only the newer AMD processors can use the cpufreq=xen. My processor can only use cpufreq=dom0-kernel. So i tried to use this. Therefore i had to recompile the kernel to get the powernow-k8.ko kernel module. A hint came from here:
http://www.ctserver.org/ftopic2437.html
but only disabling the with CONFIG_PROCESSOR_EXTERNAL_CONTROL in drivers/cpufreq/Kconfig did not do the trick. At the moment i get a compile error:

drivers/built-in.o: In function `cpufreq_quick_get':
/usr/src/linux/drivers/cpufreq/cpufreq.c:1146: multiple definition of `cpufreq_quick_get'
arch/x86/kernel/built-in.o:/usr/src/linux/arch/x86/kernel/acpi/processor_extcntl_xen.c:212: first defined here
make: *** [vmlinux.o] Error 1

I'm still investigating ...