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authorFrancis Rowe <info@gluglug.org.uk>2015-04-20 13:03:50 (EDT)
committer Francis Rowe <info@gluglug.org.uk>2015-04-20 13:05:44 (EDT)
commit8ebab158cf3d3674a96aad83cae486ed28e7d8b6 (patch)
treecdb412669b55387c0de1159f8814da5757785edf
parent5c4e59e52a3ef6fbe7b0c063736430a2b9f49295 (diff)
downloadlibreboot-8ebab158cf3d3674a96aad83cae486ed28e7d8b6.zip
libreboot-8ebab158cf3d3674a96aad83cae486ed28e7d8b6.tar.gz
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docs/git/index.html: Add more details about BUC.TS
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<p>
<b>This is for Lenovo BIOS users on the ThinkPad X60/X60S, X60 Tablet and T60. If you have coreboot or libreboot running already, ignore this.</b>
</p>
+
+ <p>
+ BUC.TS isn't really specific to these laptops, but is a bit inside the a register in the chipset on some Intel systems.
+ </p>
<p>
Bucts is needed when flashing in software the X60/X60S/X60T/T60 ROM while Lenovo BIOS is running;
external flashing will be safe regardless.
- Each ROM contains identical data inside the two final 64K region in the file.
+ Each ROM contains identical data inside the two final 64K region in the file*.
This corresponds to the final two 64K regions in the flash chip. Lenovo BIOS will prevent you from writing the
final one, so running &quot;<b>bucts 1</b>&quot; will set the machine to boot from the other block instead (which
is writeable along with everything beneath it when using a patched flashrom. see <a href="#build_flashrom">#build_flashrom</a>).
- After shutting down and booting up after the first flash,
+ After shutting down and booting up after the first flash of libreboot,
the final 64K block is writeable so you flash the ROM again with an unpatched flashrom and run "<b>bucts 0</b>" to
make the machine boot from the normal (highest) block again.
</p>
<p>
+ *Libreboot ROM images have identical data in those two 64KiB regions because dd is used to do that, by the build system.
+ If you're building from upstream (coreboot), you have to do it manually.
+ </p>
+
+ <p>
+ BUC.TS is backed up (powered) by the NVRAM battery (or CMOS battery, as some people call it). On thinkpads,
+ this is typically in a yellow plastic package with the battery inside, connected via power lines to the
+ mainboard. Removing that battery removes power to BUC.TS, resetting the bit back to 0 (if you previously set
+ it to 1).
+ </p>
+
+ <p>
BUC.TS utility is included in libreboot_src.tar.xz and libreboot_util.tar.xz.<br/>
<b>If you downloaded from git, follow <a href="#build_meta">#build_meta</a> before you proceed.</b>
</p>