https://wiki.gentoo.org/wiki/Handbook:AMD64/Installation/Media The Gentoo AMD64 project site is a good place to be for more information about Gentoo's AMD64 support. "Gentoo AMD64 project site" links to https://www.gentoo.org/proj/en/base/amd64/ but that 404s.
Actual broken page was transcluded from here: https://wiki.gentoo.org/wiki/Handbook:AMD64/Blocks/HWReqs Fixed with this revision: https://wiki.gentoo.org/index.php?title=Handbook:AMD64/Blocks/HWReqs&oldid=356998