I have run FC4 and FC5 both x86 and AMD64 versions.
All worked well.

I have amd 3800+ a8n-e x300se and fujitsu40gb usb hdd.
the system runs ubuntu 6.10 64-bit
Boots (grub)temporarly from 6.10 i386 live cd trough the option boot from
first hdd,in a previous instalation ihad selected grub to be installed
in (fd0) and it could boot with no i386 cds help [i never managed to
boot grub from the usb hdd],if i have the 64bit cd(not the live) and select boot from
first hdd nothing happens.otherwise all other is ok.
Another i like to mention is an attempt i did to install in this system
the i386 6.10 i only managad it by deleting all partitions with another
os systems cd this os tthat has much much viruses after making the instalation
of the 64bit 6.10 until the point that says configuring systems clock in which
i pressed back and then quit instalation ,open then with i386 6.10 live cd and
instaling.an attempt to install i386 from the begining didnt work only this i just mentioned.