1.4 KiB
mrc.bin
All Haswell boards supported by coreboot currently require a proprietary
blob in order to initialise the DRAM and a few other components. The
blob, named mrc.bin, largely consists of Intel's memory reference code
(MRC), but it has been tailored specifically for Chrome OS. It is just
under 200 KiB in size. Another name for mrc.bin is the system agent
binary.
Having a replacement for mrc.bin using native coreboot code is very
much desired, but it is not an easy task.
Obtaining mrc.bin
Unfortunately, it is not currently possible to distribute mrc.bin as
part of coreboot. Though, it can be obtained from a Haswell Chromebook
firmware image like so, starting in the root of the coreboot directory:
make -C util/cbfstool
cd util/chromeos
./crosfirmware.sh peppy
../cbfstool/cbfstool coreboot-*.bin extract -f mrc.bin -n mrc.bin -r RO_SECTION
Now, place mrc.bin in the root of the coreboot directory.
Alternatively, place mrc.bin anywhere you want, and set MRC_FILE to
its location when building coreboot.
ECC DRAM
When mrc.bin has finished executing, ECC is active on the channels
populated with ECC DIMMs. However, mrc.bin was tailored specifically
for Haswell Chromebooks and Chomeboxes, none of which support ECC DRAM.
While ECC likely functions correctly, it is advised to further validate
the correct operation of ECC if data integrity is absolutely critical.