Disclaimer: The BIOS should be the exact same which Lenovo published on Google Drive (state of 30.12.2020) but is (along with the guide) supplied without any warrenty. I am not liable if you brick your Laptop!
Notice (18.09.23): I apologize to anyone thinking this article was meant to be locked down behind an authwall, a config error resulted in this being the case for a brief time. I intended it to be and stay public, just like it is now (again). Again, sorry for the inconvenience.
💾 Mirrored files: https://nextcloud.libre.moe/s/Aq3cxRAWP7Ck8HZ
Secondary mirror: https://files.langrock.info/other/Lenovo Yoga C940 Beta-BIOS for Linux/
If any of these stop working, please just write me an email or something. I'll likely still have the files somewhere and will fix the links.
Download the mirrored files from the link above and extract the ZIP-archive.
Set up a USB stick with a single FAT 32 partition.
Unzip shell file.zip. This archive has the necessary files to boot your Lenovo C940 to a state that it can load the BIOS file.
Copy the resulting files and directories to the USB stick
The BIOS itself is in C940AudioTest.7z.
Use 7z x C940AudioTest.7z to unpack this archive.
Copy AUCN57WW.efi to the USB stick.
Turn off your C940.
Use Fn + Power Button to boot in to the NOLO (sp?) interface.
Press ESC to skip startup.nsh. (You only have about three seconds.)
Input fs0: to go to the USB stick directory.
Input AUCN57WW.efi to flash the new BIOS.
This guide was originally posted on the Kernel.org Bugzilla. In case this guide doesn't work as intended or you need some further assistance, it might be helpful to check out the thread there.
You can use these checkums to check if your download is identical to the files I uploaded. Please verify that the checksums are identical to make sure your download was not corrupted.
| File | MD5 | SHA1 |
|---|---|---|
| C940AudioTest (BIOS).7z | 8394a5cd417afce674a11ee7baad18a7 |
a54419d7c9682dbe6817990763bc1100b7792a83 |
| shell file (flash tool).zip | 15d6a99d4d279f28948279fe605d59c5 |
983474708085b0eca1e824e6d1501cdc21066fa0 |
These checksums were generated using Dolphin v22.04.01.