Microcode is loaded onto the CPU or GPU at boot by the BIOS, but can be replaced later by the OS itself. An update to microcode can allow a CPU's or GPU's behavior to be modified to work around certain yet to be discovered bugs, without the need to replace the hardware.
The Intel microcode package is in the non-free repo, so that has to be enabled first.
# xbps-install -S void-repo-nonfree
# xbps-install -S intel-ucode
Rebuild the initramfs matching the kernel. This only has to be done once, the
first time the
intel-ucode package is installed. If the current bootloader
configuration contains more than one kernel version, the initramfs has to be
rebuilt for each of them.
# xbps-reconfigure -f linuxX.X
The AMD package contains microcode for both AMD CPUs and GPUs. AMD CPUs and GPUs will automatically load the microcode, no further configuration required.
# xbps-install -S linux-firmware-amd
Performing the following command after a reboot can be used as verification that the update worked
$ grep microcode /proc/cpuinfo