36 lines
1.4 KiB
Markdown
36 lines
1.4 KiB
Markdown
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# mrc.bin
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All Haswell boards supported by coreboot currently require a proprietary
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blob in order to initialise the DRAM and a few other components. The
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blob, named `mrc.bin`, largely consists of Intel's memory reference code
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(MRC), but it has been tailored specifically for Chrome OS. It is just
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under 200 KiB in size. Another name for `mrc.bin` is the system agent
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binary.
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Having a replacement for `mrc.bin` using native coreboot code is very
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much desired, but it is not an easy task.
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## Obtaining mrc.bin
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Unfortunately, it is not currently possible to distribute `mrc.bin` as
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part of coreboot. Though, it can be obtained from a Haswell Chromebook
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or Chromebox firmware image, and you might find one online. `mrc.bin`
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can be extracted with the following command. If extracting from a
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"standard" coreboot image, omit `-r RO_SECTION`.
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```bash
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cbfstool coreboot.rom extract -f mrc.bin -n mrc.bin -r RO_SECTION
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```
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Now, place `mrc.bin` in the root of the coreboot directory.
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Alternatively, place `mrc.bin` anywhere you want, and set `MRC_FILE` to
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its location when building coreboot.
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## ECC DRAM
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When `mrc.bin` has finished executing, ECC is active on the channels
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populated with ECC DIMMs. However, `mrc.bin` was tailored specifically
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for Haswell Chromebooks and Chomeboxes, none of which support ECC DRAM.
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While ECC likely functions correctly, it is advised to further validate
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the correct operation of ECC if data integrity is absolutely critical.
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