AMD microcode

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This article describes updating the microcode for AMD processors.

For AMD GPU firmware see the corresponding GPU driver article instead.



Microcode updates for AMD processors are provided by sys-kernel/linux-firmware package. Install the package via:

root #emerge --ask sys-kernel/linux-firmware

Configuration (initramfs)

There are 2 different approaches to update the AMD CPU microcode:

  • microcode is build into the linux kernel
  • microcode is contained in the initramfs


The microcode is in the initrd. This way the microcode is not build-in to the the kernel.

Firmware files preparation

linux-firmware method

Enable the initramfs USE flag for sys-kernel/linux-firmware to get /boot/amd-uc.img and re-generate the initramfs.

Manual initramfs

Create the specified directory and cd into it. It might be a different dir than /tmp. The kernel/x86/microcode part is important.

user $mkdir -p /tmp/amd-ucode/kernel/x86/microcode
user $cd /tmp/amd-ucode

Concatenate the AMD firmware files into a single file. The path and filename of the output file must not be altered.

user $cat /lib/firmware/amd-ucode/microcode_amd*.bin > kernel/x86/microcode/AuthenticAMD.bin

Create a cpio archive in /boot/amd-uc.img using bsdcpio from app-arch/libarchive:

root #echo kernel/x86/microcode/AuthenticAMD.bin | bsdcpio -o -H newc -R 0:0 > /boot/amd-uc.img

GRUB2 configuration

The image file /boot/amd-uc.img is in a file path recognized by GRUB2 by default.

Regenerate the grub config using following command:

root #grub-mkconfig -o /boot/grub/grub.cfg
Found linux image: /boot/vmlinuz-4.18.12
Found initrd image: /boot/amd-uc.img /boot/initramfs-4.18.12.img

The command output should show it found the /boot/amd-uc.img file.

Kernel (Initrd)

Verify the kernel option is enabled:

KERNEL Initrd support enablement
General setup  --->
    [*] Initial RAM filesystem and RAM disk (initramfs/initrd) support

Configuration (built into kernel)

Built-in firmware

This way the firmware files will be built directly into the kernel.

Kernel (built-in)

In order to load the CPU microcode the following kernel options should be enabled:

KERNEL Enable AMD microcode loading support
Processor type and features  --->
    [*] CPU microcode loading support
    [ ]   Intel microcode loading support
    [*]   AMD microcode loading support
Modules do not work for early microcode, so make sure microcode loading is built-in.

Firmware blob files selection

Either include all the available AMD firmware files in the kernel or select just the specific one for the system's CPU.

All firmware files

Another option is to simply build all the firmware blobs into the kernel. This can be achieved by the following kernel optionsː

KERNEL All AMD firmware blobs
Device Drivers  --->
    Generic Driver Options 
        Firmware loader --->
        {*} Firmware loading facility
        (amd-ucode/microcode_amd.bin amd-ucode/microcode_amd_fam15h.bin amd-ucode/microcode_amd_fam16h.bin amd-ucode/microcode_amd_fam17h.bin amd/amd_sev_fam17h_model0xh.sbin) External firmware blobs to build into the kernel binary
        (/lib/firmware) Firmware blobs root directory
The CONFIG_FW_LOADER Firmware loading facility must be set as built into the kernel, not as a kernel module.
The CONFIG_EXTRA_FIRMWARE option allows specifying multiple firmware files by listing them space-separated.
The CONFIG_EXTRA_FIRMWARE_DIR is set to /lib/firmware, this is the default directory.
Specific firmware only

This section will only include the firmware suitable to the current system's CPU family. The CPU family identification can be obtained from /proc/cpuinfo:

user $grep -F -m 1 "cpu family" /proc/cpuinfo
cpu family      : 22

In this example the CPU belongs to the AMD CPU family 22.

The CPU family identificator listed in /proc/cpuinfo uses the decimal numeral system.
Note that after the K8 AMD has started to refer to the various microarchitectures as "AMD Family xxh", where "xxh" is the hexadecimal CPU family value from the CPUID. For example, AMD Family 10h really is the official AMD name for the K10 microarchitecture. Following this convention AMD is even using AMD Family 0Fh for the previous K8 microarchitecture (CPUID 0F hexadecimal or 15 decimal).

The following table helps to identify the right firmware blob file for given CPU family identificator:

Firmware blob file Decimal Hexadecimal Family name Year Examples
amd-ucode/microcode_amd.bin 16 10h K10 2007 Phenom, Phenom II, Athlon II
17 11h Turion 2008 Athlon X2, Sempron X2, Turion X2
18 12h Llano, Fusion 2009 A- and E2-Series APU with Radeon HD graphics, Athlon II, Sempron X2
20 14h Bobcat 2011 C- and E-Series APU with Radeon HD graphics
amd-ucode/microcode_amd_fam15h.bin 21 15h Bulldozer, Piledriver, Steamroller, Excavator 2011 FX series, A-Series APU with Radeon HD graphics, Opteron 6200/6300
amd-ucode/microcode_amd_fam16h.bin 22 16h Jaguar, Puma 2013 A-series and E-Series APU with Radeon HD graphics
amd-ucode/microcode_amd_fam17h.bin 23 17h Zen, Zen+, Zen 2 2017 Ryzen 1000-4000 series, Threadripper, EPYC 7xx1/7xx2
  amd/amd_sev_fam17h_model0xh.sbin EPYC 7xx1[1] (Zen 1) 2017 SEV (Secure Encrypted Virtualization) firmware update for models in the range 00h to 0fh[2]
  amd/amd_sev_fam17h_model3xh.sbin EPYC 7xx2[3] (Zen 2) 2019 SEV firmware update for models in the range 30h to 3fh[4]
amd-ucode/microcode_amd_fam19h.bin 25 19h Zen 3 2021 Ryzen 5000 series (not all models), EPYC 7xx3
  amd/amd_sev_fam19h_model0xh.sbin EPYC 7xx3[5] (Zen 3) 2021 SEV firmware update for models in the range 00h to 0fh[6]

The previously identified CPU specific firmware blob file (in this example CPU family 22) needs to be built into the kernelː

KERNEL Single AMD firmware blob
Device Drivers  --->
    Generic Driver Options 
        Firmware loader --->
        {*} Firmware loading facility
        (amd-ucode/microcode_amd_fam16h.bin) External firmware blobs to build into the kernel binary
        (/lib/firmware) Firmware blobs root directory
The CONFIG_FW_LOADER Firmware loading facility must be set as built into the kernel, not as a kernel module.

Rebuild the kernel

Rebuild and install the kernel as usual.


After the next reboot with the new kernel, output similar to the following should be observed:

user $dmesg | grep microcode
[    0.584603] microcode: microcode: updated early to new patch_level=0x06000832
[    0.868036] microcode: CPU0: patch_level=0x06000832
[    0.868116] microcode: CPU1: patch_level=0x06000832
[    0.868196] microcode: CPU2: patch_level=0x06000832
[    0.868277] microcode: CPU3: patch_level=0x06000832
[    0.868360] microcode: CPU4: patch_level=0x06000832
[    0.868451] microcode: CPU5: patch_level=0x06000832
[    0.868538] microcode: CPU6: patch_level=0x06000832
[    0.868619] microcode: CPU7: patch_level=0x06000832
[    0.868718] microcode: Microcode Update Driver: v2.01 <>, Peter Oruba

The first line contains the microcode: updated early log message in case a microcode update was performed during the boot.

It is possible the microcode has already been fully updated by the system's BIOS vendor. In that case the dmesg output does not contain the update log message.