This post was originally available on Reddit but is no longer available. It is replicated here because it has helped save a number of people from having to RMA their Steam Deck. The original post also supplied a ‘cleaned’ BIOS file. Unfortunately it was stored on a Google Drive and the file has been removed.
So you, like me, went too hard on the undervolting and ended up bricking your SD. And worst, you didn’t make a backup of your BIOS beforehand?
Fear not, it’s is possible to recover your SD even without a BIOS backup, I just did it to mine.
You’re going to need a CH341A SPI chip programmer. More details on how to use it, please refer to this guide by /u/Interesting-Bag-6206:
Here there’s another guide on how to read and write the BIOS on windows and Linux https://jensd.be/980/linux/bios-or-spi-programming-on-windows-or-linux-using-a-ch341a
Download the bios file direct from here: https://gitlab.com/evlaV/jupiter-hw-support/-/tree/master/usr/share/jupiter_bios
Editor’s Note: You should download a BIOS version higher than 110 unless you have an EV2 device.
Unzip the file and go to /usr/share/jupiter_bios/ open F7A0115_sign.fd using a HEX editor. In my case I’m using Bless, for linux. This is what you’re going to see:
Search for $_IFLASH_BIOSIMG and delete everythign before ….( 02 02 00 02 28 in hexadecimal
This is what should look like. The first 5 hexadecimal digits should be 02 02 00 02 28 like in the picture below.
Then go to line 00ffffec on your hex editor. Delete everything after the last FF.
This is how it should look like after
Save the file, this is the “clean” file I’m making available above.
You need to dump your “corrupted” bios using the guides.
DO NOT UNDER ANY CIRCUMSTANCE OVERWRITE YOUR BIOS BEFORE DUMPING IT
You will need your original BIOS file to be able to restore your deck. If you overwrite it now with the “clean” BIOS is GAME OVER.
Open your corrupted bios and make sure you have more than 1 backup of it just in case. You’re going to see a familiar sight.
Search for $DMI on the hex editor (line 006a3fce).There are only 2 places where it appears. The first one is what you want. You Are going to see a block of info’ containing your Deck serial number, Controller ID, etc. Copy the entire block. It’s easy to see. It starts after an FF and ends before an FF.
Open your “clean” BIOS file and replace the exact block, this is exactly what you have to replace
Save your modified BIOS, and write it to the Deck. That’s it! It will take about a minute to boot the first time. After that it should be back in working condition.
DISCLAIMER: I’m not responsible for any damage you cause to your deck.”
This article was recovered via the web archive.
You can find more information about overclocking, undervolting and backing up your BIOS in my other blog post.