[arch-general] What are the dual isos about?

Hi, I've found the following link, which seems to contain more up to date images of archlinux and the installer: http://build.archlinux.org/isos/ Now I'm wondering what these dual images are about? Is this a new architecture? Whats the difference to x86_64 in that case? How is the support for packages? Thanks in advance! -- Best regards, Karol Babioch <karol@babioch.de>