Comment 150 for bug 1671360

Here is a 4 steps procedures that worked on AB350 Gaming 3 Ryzen 1600 (F4 bios) to get 17.04 with all cores and threads

1)Ubuntu 17.04 install from usb bootable drive with acpi=off (press F6 when display menu)

2)log in and install sudo dpk -i *deb the kernel compiled by nextized worked:
http://www.nextized.net/repo/linux/ubuntu-linux-4.10.3_ryzen01_amd64_generic.tar.gz
3) push back acpi=on to your 17.04 system to get all core and threads from your Ryzen
sudo gedit /etc/default/grub
Change line GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" to GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=on"
sudo update-grub
4) reboot and you should have all cores and threads on 17.04 new install