Quad Xeon, 8GB memory (960M used by Linux). The installer fails to boot: the initrd cannot be loaded, giving the error initrd extends beyond end of memory (0xfeff9433 > 0xfc000000) 5.8 cdrom and floppy installs did not have this problem. 5.9 and all subsequent betas do. Booting with "linux mem=512m" is a workaround.
We are aware of this limitation. The installer is only capable of running on < 1G of RAM, so the workaround is to boot the machine with a mem= line and perform the installation. After installation, the running machine will be able to make use of all RAM that you have in the system.