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Installing GAMMA

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veerserif edited this page Jun 10, 2026 · 20 revisions

Introduction

The most up-to-date and detailed version of these instructions will always be on the GAMMA Discord's #how-to-install channel. This also goes for any install links.

This guide only covers installing GAMMA on Windows x64. For other OSes:

Dependencies

Base requirements

  1. 7-Zip. WinRAR and Windows's default archive manager are known to cause issues when extracting large .7z files. Use 7-Zip for all file extraction when installing GAMMA.
  2. At least 150GB free disk space for all install files, Anomaly, and the modpack. You must have at least this much space to start and finish the installation process before you think about "trimming" the install size. Ideally you would have about 175-200GB free to minimize the chance of errors.

Preparation

  1. Download key installation files:
Anomaly 1.5.3 archive

This contains the Anomaly game files, which is a standalone fan-made STALKER game originally based on the STALKER Call of Chernobyl mod.

Mirror Download Link
Official Torrent download Magnet Link
Moddb direct download https://www.moddb.com/mods/stalker-anomaly/downloads/stalker-anomaly-153
GAMMA RC3 archive

This contains all the key files for the GAMMA modpack including Mod Organizer 2. Pick only one mirror link, they all correspond to the same file.

Mirror Download Link
Gofile https://gofile.io/d/Y8NnGS
Mediafire https://www.mediafire.com/file_premium/xgldcs2qbzpcz20/GAMMA_RC3.7z/file
MEGA https://mega.nz/folder/xeUC3TJa#D2tWBrPrKi64Kq_S4CCYrg
FuckingFast https://fuckingfast.net/y3bpx53eou4n
  1. Create a GAMMA folder and an Anomaly folder. These must be:
    • Two different folders, not inside each other
    • Not in any restricted location e.g. in your Users folder (this includes Documents), Desktop, OneDrive, Program Files, etc.
    • On the same drive
    • Not on an external hard drive (connected to a USB port)

For instance the GAMMA folder F:/STALKER GAMMA/GAMMA and the Anomaly folder F:/STALKER GAMMA/Anomaly

If you already have a STALKER Anomaly folder, make sure it is clean and unmodded and in 1.5.3 version

  1. Make sure the GAMMA folder and Anomaly folder are in antivirus exclusions.

Due to its folder virtualization system, MO2 is frequently blocked by antivirus. Put these folders in antivirus exceptions before you start extracting or downloading anything.

  • Certain antivirus programs are known to block the launcher downloads. If you have one of them, you will need to disable them completely while the GAMMA Launcher is installing. You can re-enable them afterwards.
  • These include: Norton, Avast, AVG, Malwarebytes
  • Bitdefender tends to block MO2 as well as all the Anomaly executables. All of these .exe files must be individually excluded from Advanced Threat Defense.
Optional: Verifying downloaded files

SHA256 checksums for the downloaded files are as follows. Open a Powershell window in the directory where these files are, run CertUtil -hashfile "filename" SHA256, and make sure the hash exactly matches the provided checksum.

File SHA256 checksum
Anomaly-1.5.3-Full.2.7z E564D9110E673EACFA5604B0837F6E6208EAE4CD46CD5682326ED59F931527AE
GAMMA RC3.7z 2ceda1782b0b7737747c16974f1fe014bc1915caf1b08a1cba71e7950485192d

Last updated 2025-12-06 15:32.

Installation

  1. Extract the contents of the Anomaly 1.5.3 archive to your Anomaly folder.
  2. Run AnomalyLauncher.exe and click Play until you are at the main menu, then exit out of the game.
  3. Extract the contents of the GAMMA RC3 archive to your GAMMA folder.
  4. In your GAMMA folder, open the .Grok's Modpack Installer folder and run the G.A.M.M.A. Launcher.exe program.

Make sure the GAMMA Launcher says v8.6 in the top left part of the window. If not then follow the steps in the Update the GAMMA Launcher section below.

  1. Click "First Install Initialization". You only have to do this once.
  2. When Mod Organizer asks you what game to manage, select your Anomaly folder (the one that contains AnomalyLauncher.exe). Close the Mod Organizer window.
  3. Leave all GAMMA Launcher options on default, and click "Install / Update GAMMA".
  4. Once the green launcher window displays the "Installation finished" message, click the Play button to launch Mod Organizer 2.
  5. In Mod Organizer 2, pick "Anomaly (DX11)" in the top right corner dropdown menu, then click the "Run" button to launch GAMMA.

The GAMMA Launcher creates a shortcut to both the GAMMA Launcher and Mod Organizer 2 on your desktop. You can use these to run the game or the launcher.

Updating the GAMMA Launcher

If your GAMMA launcher is not up-to-date, you need to update it manually:

  • Get the GAMMA Launcher v8.6 on Mediafire
  • Extract its contents to your GAMMA/.Grok's Modpack Installer folder, overwriting when asked

Troubleshooting

Less than the expected number of mods

  • Make sure you have Anomaly and GAMMA in antivirus exclusions
  • Temporarily disable antivirus for the duration of install
  • Make sure you have the most up-to-date version of the GAMMA Launcher
  • Open GAMMA Launcher and click 'Install / Update GAMMA' again

Playing on different DX versions

  • DX11 has the best mod compatibility and looks the best. We always recommend running DX11 if your PC can handle it.
  • DX10 is broken, do not run it
  • DX8 and 9 have worse compatibility and visuals, but have better performance. If you want to play GAMMA on DX8 or DX9, you must get and use the DX8/9 modlist.

I have metered internet, how much will I be downloading?

Sizes are approximate to the nearest GB.

File(s) Download size Installed/Extracted size
Anomaly 1.5.3 9 GB 16 GB
GAMMA RC3 11 GB 27 GB
GAMMA mods via launcher 27 GB 76 GB

The total installed size of GAMMA (not including Anomaly) is around 130 GB, including downloaded files, Git-pulled files, and so on. This comes from the 27GB installed size for GAMMA RC3, the 27GB of downloaded mod files, and then 76GB for the installed mods.

How can I save hard drive space after I install GAMMA?

Deleting the original install archives can save some space, about 20 GB. You can also delete all mods in the "GAMMA Disabled (do not activate)" and End of List categories in Mod Organizer 2.

You should only delete the archives in GAMMA/downloads at your own risk. If you ever need to repair the modpack, update GAMMA, or reinstall it, you will be forced to redownload ALL of those files, and the process will fail if you don't have enough space for them.

Uninstalling GAMMA

To uninstall GAMMA and Anomaly, just delete the GAMMA and Anomaly folders. Neither game saves anything outside of their folders.

Support GAMMA

You can support GAMMA by making donations through PayPal: https://www.paypal.com/paypalme/GrokitachGAMMA

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