Okay you should do this in stages. The first thing we should do is upgrade your kernel to something more recent and AMD friendly.
Lets install the Voodoo kernel.
Download the voodoo kernel from here.
http://xnu-dev.googlecode.com/files/..._1.0_Rev_A.dmg
Im not a fan of Installers I like to know what being done and know that it was done correctly. Feel free to use the installer but at your own risk. I have also included the commands to do it manually. Don't let me scare you away with a pile of commands. Its not that many I just like to explain each in detail so that people can learn what they are doing instead of typing mindless lines of code.
Once you finish and have restarted check your kernel version as mentioned earlier by using the uname -a command. It should say Voodoo. Let me know once you have gotten this far.
Manually installing a kernel
You can manually install install a kernel by following the instructions below. In order for the system to work properly you will need to have a kernel & system.kext with matching versions. Hopefully you already know which kernel version you have downloaded and generally these packages include a matching system.kext. If you would like to
1. Make a backup copy of your existing kernel and name it mach_kernel.backup
Code:
cp -r /mach_kernel /mach_kernel.backup
2. Copy the new kernel from your USB thumb drive to the root directory
Code:
cp -r /Volumes/usbdrive/mach_kernel /mach_kernel
3. Correct ownership for all kernels
Code:
chown root:wheel /mach_kernel*
4. Correct permissions for all kernels
Code:
chmod 644 /mach_kernel*