IMAGE_UCODE
Configured via config/general.h.
#define IMAGE_UCODE /* Microcode update images */
chain --autofree http://192.168.0.1/ucode.bin
chain --autofree http://192.168.0.1/ucode.bin --verbose
This build option enables support for Intel and AMD microcode update images.
You can apply microcode updates before booting an operating system, to ensure that the latest microcode is in use even if the operating system itself has not yet been updated.
Intel microcode updates are published to the Intel Processor Microcode Update repository, and AMD microcode updates are published as part of the linux-firmware repository. Both are included within most Linux distributions, and can usually be found in the /lib/firmware/intel-ucode and /lib/firmware/amd-ucode directories.
iPXE will automatically identify the appropriate update to use for your processor within the update file. You can concatenate any number of microcode updates into a single file for ease of use. For example:
cat /lib/firmware/intel-ucode/*-*-* /lib/firmware/amd-ucode/*.bin > ucode.bin
To reduce download size, you can also create separate files for each CPU vendor. For example:
cat /lib/firmware/intel-ucode/*-*-* > GenuineIntel.bin cat /lib/firmware/amd-ucode/*.bin > AuthenticAMD.bin
You can then use the cpuvendor setting in iPXE to download the appropriate per-vendor file:
chain --autofree http://192.168.0.1/${cpuvendor}.bin
By default, executing a microcode update image will produce no output unless an error occurs. You can obtain a brief summary status report by using the --verbose option. For example:
iPXE> chain --autofree http://192.168.0.1/ucode.bin --verbose Microcode: updated version 0x4114->0x411c (x12)
This one-line status report shows the old and new microcode versions and the number of CPU cores updated.
In almost all cases, you will want to free the download microcode image after applying it. You can either use the --autofree option as shown above, or use the imgfree command to explicitly free the microcode image.