Okay, this is seriously confusing me. I have been reading a lot about Snow Leopard in prep for tomorrow, but getting an answer for this seems pretty difficult. I apologise if this has been covered in one of the big Snow Leopard threads, but every time I look at them they gain 10 pages of posts and it's hard to find anything. So, with Snow Leopard, there is a 32-bit kernel, and a 64-bit kernel. Correct? As I understand it, it will boot into the 32-bit kernel by default, but if your hardware is supported, you can select the 64-bit kernel. My question is - where is the list of supported hardware, and how do you select the 64-bit kernel? My confusion comes from several posts and various articles which all say the first-gen aluminium iMac has a 32-bit EFI, and therefore can only boot into the 32-bit kernel. But I've just downloaded an app called Startup Mode Selector, which shows you your system config, and it says I have a 64-bit EFI. Assuming this app is reporting correctly, that means my iMac can boot the 64-bit kernel, and that at least three supported hardware lists that I have seen are incorrect. Can anyone help out here and clear up the confusion?