Intel microcode

This article Article description::describes the process of updating the microcode on Intel processors.

Kernel
You need to activate the following kernel options:

Software
You can now install the microcode

And a tool to manipulate it

Configuration
After emerging, generate the microcode cpio archive using :

Syslinux
multiple initrd file separate by commas, early_ucode.cpio load first

GRUB Legacy
Add the generated microcode to your kernel command line as an initrd parameter (this should be done even if you don't use an initrd image in order to boot, the microcode update merely leverages the initrd hooks):

GRUB
Change this small section of from:

To this:

Regenerate the with:

Reboot and you're all done.

rEFInd
This example system has the EFI partition mounted to. The Linux kernel and initrd files have been placed in on the Linux rootfs.

If you are using the initrd keyword instead of the options keyword for specifying initrd, then try specifying multiple initrd files via separate initrd keywords, or migrate the declarations into options. Specifying multiple initrd via one initrd keyword fails on rEFInd. As always, make sure is the first initrd specified.

You can review and edit the kernel cmdline options from the rEFInd bootloader. With your Gentoo OS entry highlighted, press F2 to access the menu entries, and press F2 again over the desired entry to review and edit. This is very useful for quick experimenting without need to edit.

See for keyword descriptions and The rEFInd Homepage for more on how to use rEFInd.

systemd-boot
Add the microcode as an argument to an initrd line. If you already have an initrd line, ensure the microcode line occurs first. The path to the microcode should be absolute to the root of the ESP.

For more information, see The Boot Loader Specification.

Xen (EFI)
Add a line to your xen.cfg with the 'ucode=' option. The path to the microcode is relative to the xen.efi binary, so you will need to write the microcode into the correct location (default is /boot/EFI/Gentoo) or copy it there.

For more information, see the Xen EFI documentation.

Verification
Here is an example of a CPU with no available microcode updates or the system was not configured to load them properly:

Here is the same CPU but with microcode updates being applied successfully:

Kernel
Activate the following kernel options:

Software
Install :

OpenRC
Start microcode-ctl:

To start microcode-ctl at boot time, add it your boot runlevel:

systemd
See: Systemd. Simply make sure that the Microcode loader is set as a module in the kernel configuration as noted above. You don't need to add a service or do anything else.

Software
You can install the officially published microcode package and let it automatically processed by

And you can use this tool to identify your actual CPU signature(s)

To find the appropriate filename(s) for the listed signature(s) use:

The signature found in the microcode bundle 49, so the filename to use is intel-ucode/06-3c-03

Kernel
You need tho enable and configure the following kernel options:

Rebuild and install the kernel as normal.

Verification
After the next reboot, you should see something like this:

External resources

 * http://www.win-raid.com/t154f16-Tool-Guide-News-quot-UEFI-BIOS-Updater-quot-UBU.html - An example unofficial source for microcodes