I will try to explain one more time:

1. Create Back-Ups of your old Kernel & Extensions:
2. Ensure to have a Disabler beeing installed - i.e. Disabler.kext or NullCPUPowermanagment.kext - there are even patched Kernels with integrated Disabler, but it doesn't hurt your System to have both.

3. Download and apply the Update & reboot

4. Boot your System using "/bak_kernel -v" on the bootprompt.

5. Delete new Vanilla Kernel and replace it with your legacy kernel:I have no problem using 10.6.3 with 10.2.0 XNU & 10.6.3 System.kext - so I wouldn't copy over old Kernel Extensions until you expire different.

6. You might want to reinstall old AppleHDA kext if you had been using it but lost Sound with the update.

7. Use Marvin's AMD Utility - create a CPUID text file using Patcher Package option, for /System/Library folder - exclude any Kernel Extensions & encrypted files (find them in decrypt folder) from the text file - save the text file under a different name & patch CPUIDs by dissabling simulation mode - AMD Utility will succed but crash - Kill it using Apple Menu option and reboot.

8. If any other problems occur try to repair permissions for /S/L/E and delete /System/Library/Chaches/com.apple.kext.chaches

Could you please post that 10.6.2 AppleHDA kext here please? I forgot to do that and loose my sound after the update :(

Did it like Snow

- Removed Sleepenabler Kext & Downloaded v10.6.3
- Performed update via Combo Update
- Placed Sleepenabler v10.6.3 kext in Extra folder
- Ran pfix (to repair Extensions and create mkexts in both S/L/E & Extra)
- Updated sig ;)
- Done

Just did it and it works perfect =)

Snow Leo 10.6.3 on XFX GeForce 9300
 

1st. - Preparation: Saved my Kernel (Blacknight)
make a Carbon Coby Clone

2nd: - Download and install

3rd: - Reboot
Before rebooting: exchange the 10.6.3 original kernel (back to Blacknight 10.6.2)

4th: - Everything correct?
No, sound is absent - but no problem

Over all time for cloning, downloading and new installation approximately 1 hour.

Best regards.

P.S.:

System:
Mainboard: XFX GeForce 9300 (no extra graphic card)
CPU: Intel Core 2 Duo E8400
RAM: 4GByte Kingston
Harddisk: 160 Gbyte Samsung

Special OSx86 enviroment:

PC-EFI 10.6 bootloader
in extra/extensions: AppleIntelPIIxATA.KEXT
AppleIntelPIIxATA2.KEXT
in systems/library/extensions: AppleAHCIPort.KEXT (modified for 9300)
AHCIPortInjector.KEXT
ElliotForceLegacyRTC.KEXT
EvOreboot.KEXT
Fakesmc.KEXT
NVInabler.KEXT

Problem since update
 

It seems the my gfx performance has gone to the dogs since i update, im using the ati 4850 1gig, I backed up the needed kekts etc for my ati before doing anything and then put them back as described on netkas.org, desktop seems slow almost stuttering to bring up icons, while with I-Tunes the Visualizer dont work anymore.
Any got any ideas.
System specs in my sig.

IMKANTUS
can you please tell me more about that amd patch process , i have some problems, i dont get it, i press "create patcher package" then app found about 3080 files to patch, what do you men by "System/Library folder - exclude any Kernel Extensions & encrypted files (find them in decrypt folder) from the text file - save the text file under a different name"

can you please tell me more about this, because now my itunes is crashing and full patch all binaries option is not working

thank you

Sure i can. :)

Open Marvins's AMD Utiliy, select "Create Patcher Package", press "browse and select "/System/Library" folder. It will take it's time and create "AMD.Patch.Folder/XXXX.XX.XX_at_XX:XX" folders on your Desktop. They will contain a folder named "decrypts" and text file called "cpuid" - copy cpuid to your desktop and open decrypts.
Open the cpuid file you just copied to your desktop with an text editor of your choice and remove all the lines with CPUIDs that had been found in /System/Library/Extensions for example remove:Next have a look at the files placed in the folder named "decrypts" and remove them from cpuid file as well - for example SystemUIServer is in decrypts folder so you'll remove the following lines:After you're done save the text file and go back to Marvin's Utility: select the "Patch all cpuid's using cpuid file" option - remove the Simulation Mode - select the edited cpuid file from your Desktop and /System/Library as destination and let it do it's magic.
Atfer that iTunes, Spotlight, Photoshop & Co should be fine again. :)

thank you so much imkantus :) done everything and got smooth working amd system again, but geekbench score is a bit lower than it was before, but in everyday computing experience i cant feel differences in bad way :)

anyways thank you again, happy to see some helpful people around here

Is ATI4870 supported?
 

Does anyone know if there are any issues with the patch on a Intel DX58S0 / i7-920 / ATI 4870? I read something about the AppleHDA sound Kext, having a issue, but that does not bother me because i can just reapply it afterwards. The Only concern that i have is the video.

Just in case does anyone know what the terminal command is to rollback os to use pre patch version?

Just thought I'd throw in my 2 cents about the kernel. In the new update a new kernel is installed. What I have always done to protect myself from having the working kernel wiped was; I renamed the mach_kernel to another name such as legacy_kernel, then in the com.boot.plist file located in the extra folder I entered the following.
This makes it so if you ever install an update your custom kernel will never get overwritten with the new vanilla one provided by apple and the system will always use it.