I have pxe install server with syslinux. Works fine for both i386 and amd64 FreeBSD 8.2 with that conf.
FreeBSD 9.0 amd64 can't boot.
Code:
label fb82
menu label FreeBSD 8.2
linux memdisk
initrd [url]http://1.200.0.1/images/fb82.iso[/url]
append iso raw nfsroot=1.200.0.1:/data/tftpboot/freebsd/8.2
label fb82_64
menu label FreeBSD 8.2 64-bit
linux memdisk
initrd [url]http://1.200.0.1/images/fb82_64.iso[/url]
append iso raw nfsroot=1.200.0.1:/data/tftpboot/freebsd/64/8.2