How to Install Fallout Et Tu Mod on Steam Deck

I originally wrote this guide on Reddit a little while back. I saw a heap of posts about getting the original Fallout game to run well on the Deck. I didn’t really see any guides though. I’d just installed the mod so I thought I’d write one myself. This was shortly after the TV show came out, so Fallout was the in franchise.

Yes, you can just install and play Fallout from Steam off the bat. It will run well enough on its own without any mods. I really think the best way to play the original Fallout is via the Fallout Et Tu mod. This runs Fallout 1 in the Fallout 2 engine. There’s a good amount of quality of life fixes in the Fallout 2 engine that makes it worthwhile.

I did run into issues getting undat.sh/exe to work properly on the Steam Deck on the first go around. I don’t really remember why. I did the workaround at the end of this guide, which you can do if you prefer. I have since been able to get undat.exe to work running through WINE and launch without issue. I haven’t had any luck with undat.sh.

This guide does assume that you have installed WINE on your Steam Deck. You could attempt this guide with one of the other tools like Bottles, Winetricks or possibly even Lutris. I ran into issues with Winetricks and I haven’t tried the rest. WINE worked without issue the last time I installed the mod, so I haven’t deviated from that.

If you do run into issues using undat, please see under the below steps for a workaround. Windows or Mac required.

Complete the following to install the mod:

1. ⁠Install Fallout 1 and 2 on your Steam Deck.
2. ⁠Swap to desktop mode and head to the Fallout Et Tu GitHub and grab the latest release.
3. Place the Fallout1in2 folder in your Fallout 2 game folder.
4. Run undat.exe with WINE(Right-click and select ‘Open With’) and navigate to your Fallout 1 install folder and select MASTER.DAT. Click extract and once finished, click done. You can uninstall Fallout 1 at this point.
5. Right-click on fallout2.exe in the Fallout1in2 folder and select Add to Steam.
6. While in the Fallout1in2 folder, edit the f2_res.ini file and update the following settings:
   
   GraphicsMode=0
   SCR_WIDTH=960
   SCR_HEIGHT=600
   SCALE_X2=0
   
   You can update these to whatever you like. I found this to be the best for me. At the very least, it didn’t make my eyes burn like 1280×800 did.
7. While still in the Fallout1in2 folder, edit the ddraw.ini file and update the following settings:
   
   HiResMode=1
   [Graphics]
   Mode=4
   GraphicsWidth=0
   GraphicsHeight=0
   
8. Go back into Gaming mode and head to Non-Steam games. Select Fallout2.exe, navigate to the settings icon and select ‘Properties’. Here you can re-name this shortcut whatever you like in the shortcut tab. I went with Fallout Et Tu.
9. Don’t launch the game just yet. If you do launch it now, the shortcut will launch Fallout 2 vanilla. You’ll need to add a launch option in the shortcut tab so it can properly inject the ddraw.dll file for Fallout Et Tu to run. Add the following without quotation marks: “WINEDLLOVERRIDES=‘ddraw.dll=n,b’ %command%”
10. Head into the Compatibility tab and ensure ‘Force the use of a specific Steam Play compatibility tool’ is ticked. You will need to have some form of proton selected or the game will not run. I’m using GE-Proton9-2.

Fallout Et Tu is now be ready to launched. You’ll know if it’s successful if you see ‘Fallout Et Tu’ in the bottom right hand corner of the menu.

I highly suggest toggling off frame limiting via the graphics options in the quick access menu on the Steam Deck. While toggled on, it’ll run quite slow and generally make you feel sick after a few minutes. But each to their own, I guess. I also limited TDP to 3 and graphics clock to 200mhz, but either aren’t overly necessary. Saves you a good amount of battery, though.

Controls wise, I had this set to the default ‘mouse only’ template and added a few bits and pieces. I’m using the right trackpad for the mouse, L2 for right click, B for Esc, and Y button for inventory. Setup your control scheme for whatever feels comfortable for you.

Workaround:

More or less, the workaround is to install the mod on Windows or Mac and copy the install across to your Steam Deck.

1. Follow steps 1-4 above on an alternate Windows PC or on a Mac via Crossover/Whisky/Virtual Machine. Running undat.exe here should be pretty straightforward.
2. Install Fallout 2 on your Steam Deck
3. Copy the Fallout1in2 folder from your alternate computer
4. Paste the Fallout1in2 folder into your Fallout 2 install folder on your Steam Deck
5. Continue the above steps from Step 5

The same/similar steps will work for the GOG version of the game as it is DRM-free. I’m unsure about Epic Games, but likely this will be similar if not the same.