Snow Leopard ICH8-R

9/3/09 Edit: I found the answer, thanks to frantisheq on the XPS410 thread on Insanelymac. Quite simple, actually. Snow Leopard needs to be SATA0 to load AHCI properly. That means that SL didn't like me loading AHCI devices when running from a USB drive, and it didn't like frantisheq loading AHCI devices when running from SATA1. This really won't be a problem for many people, though it is annoying if you like to have two drives (one with a test installation). It would still be nice to have "fixed" but maybe that's not feasible. I'm happy enough just to be booting from the HD!

It appears that some, if not all, ICH8 boards in RAID (AHCI) mode have some preliminary issues with Snow Leopard. I own a Dell E520 and have been trying to track this issue down, this is what I've got so far:

• The problem lies with ATAPI and does not appear to affect hard drives. So, if you are installing from a USB drive, you can get Snow Leopard working in AHCI by disabling the CD/DVD drives. Obviously, this is not a permanent solution but merely a temporary one that provides an easier way of further testing.
• I suspect SCSITaskUserClient.kext (plugin of IOSCSIArchitectureModelFamily.kext) to be the culprit. Seems like the ATAPI drives initialize correctly, SCSITaskUserClient attaches to the last ATAPI drive, and then stalls when another process asks for information about ATAPI. That requesting process could be Finder, System Profiler, Disk Utility, etc. Up until that time, everything is "reported" as being correctly loaded by IOReg.
• Running in 32 bit and using Leopard kexts has not got me anywhere yet. Apparently a Leopard SCSITaskUserClient wants a Leopard IOAHCISerialATAPI, and that mouse wants a cookie. Reverting to Leopard isn't a real solution anyway.

I've been searching for solutions to this, and asked on the IRC, nobody seems to have an answer they would mention. Any thoughts?

theStevo