1) If I build and boot a 32-bit version of Gentoo it is my understanding that the AMD64 will be completely 32-bit compatible and that I can run whatever any other IA-32 machine can run. Is this correct?
Yes
2) If I build a 32-bit install is there anyway to run this 32-bit environment within the 64-bit environment? I assume not.
Yes, using a chroot -- [email protected] mailing list
