Hi, I've got a mid-2007 C2D MBP with 64-bit EFI and obviously, 64-bit processors. '6' and '4' on Snow Leopard won't boot into 64-bit mode. I don't need the 64-bit kernel at this point, but I'm mostly curious to see what drivers and apps breaks under a 64-bit kernel and the only way to find out is to try it. There's a pretty nifty hack involving hex editing boot.efi that works for some suitable Macs: http://www.osxbook.com/blog/2009/08/31/is-your-machine-good-enough-for-snow-leopard-k64/ No mention of MBP, and my attempts at guessing offsets and values while hex editing didn't cause any booting issues but didn't result in 64-bit kernel loading, either. Anybody happen to know offset and value in boot.efi to mod for a MBP? I know this is a real long shot type of question and I'm not expecting anybody to know. But if you do, would love to find out.