Originally Posted by Logisticaldron
The ability to run the 64-bit kernel is based on more than having a 64-bit CPU. MacBooks and MacBook Pros with only the Nvidia IGP will not have the 64-bit kernel option, and i don’t think older MBPs will get the option as well.
That would be unbelievably foolish on Apple's part. 64bit means 1 thing: larger addressing space. This applies to a number of different things, most visible to the *consumer* would be ram, but all are important. Additionally, we gain a large speed increase on x86 moving to 64bit because AMD took advantage of the move to 64bit to add more registers to the spec for AMD64 (which intel kept in their version, EM64T).
The ability to run a 64bit kernel and execute 64bit compiled programs should not be effected by the the IGP at all, it doesn't touch it. Additionally, having even a 32-bit chipset (like my 2.33 MBP) shouldn't be a problem except that the *chipset* will limit addressable memory to ~3.2GB. I run a pure 64bit copy of debian on my MBP already and if Apple were truly foolish enough to not support 64bit on it in MacOS 10.6 I would be astounded.
In short, it's possible that select models in the dev builds had 64bit off because they hadn't compiled a kernel for that model that was 64bit yet (or select builds did, or the machine was booted into a 32bit kernel because of a bug, or... etc), but I *really* doubt that any machine with a 64bit proc won't be supported with a 64bit kernel in the optical release.