Cemu

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Cemu
Cemu-Logo.png
Developer(s) Exzap, Petergov
Latest version 1.15.0e
Active Yes
Platform(s) Windows
Architecture(s) x86_64
Emulates Wii U
Website Cemu
Support ($) Patreon

Cemu is a closed-source Wii U emulator for Windows. It is known to be the very first Wii U emulator ever that can boot games. A compatibility list can be found here or here.

Before updates are publicly released, they're accessible to backers over at their Patreon.

Downloads[edit]

System requirements[edit]

You will also need enough storage for the Wii U games. Running Cemu on Wine has been reported to work just as well as Windows.

Minimum[edit]

  • Windows 7 (64-bit)
  • Graphics Card: Supports at least OpenGL 4.1
  • Memory: 4 GB

Recommended[edit]

  • Windows 10 (64-bit)
  • Graphics Card: Supports OpenGL 4.6 (avoid integrated graphics)
  • Memory: 8 GB or more

Game Formats and Files Needed[edit]

Physical Dumps[edit]

You'll first need to fill in the "keys.txt" file in Cemu's directory. It has a sample line with a bogus key and a comment, which you may as well delete.

Your file must have many lines like this, one for the Wii U Common Key (D7B00402659BA2ABD2CB0DB27FA2B656), and one line for the Game Key of each game. Sharing these keys isn't exactly safe legally, but ROM sites at least share the Game ones. Note that for games using the Loadiine format, you won't need a Game Key at all, but those will need Cemu versions from 1.4.0 onward.

Your ISO must be either uncompressed, compressed using WUD format, or in Loadiine format (only possible for versions 1.4.0 onward) to boot in Cemu. Here's a compatibility list. Dump your discs using Wudump.

Digital Copies[edit]

Cemu supports either physical games dumps in WUD, or compressed WUX format, as well as game dumps converted to the Loadiine format. Loadiine games come as multiple directories with game files and a .rpx file.

Nintendo's servers are poorly secured due to a huge oversight when designing Wii U/3DS software protection. As such, with tickets proving you bought the game (but which you can get through less legit ways), there are downloader utilities like NUSGrabber, FunKiiU, UWizard, or jnus among others, and decryption tools like UWizard and CDecrypt, to obtain a functional copy. The process of how to exactly acquire those files is detailed elsewhere on this wiki.

Load the .rpx file from [Your gamelocation]/code/[yourgame].rpx with Cemu.

Updates and DLC[edit]

Prior to 1.7.3, only updates were supported though pasting update files on the main game's folders (keeping in mind the main game is in Loadiine format) and overwriting any files. DLC wouldn't work at all through this method, though with some specific games there were workarounds and some could play DLC tracks in Mario Kart 8 through swapping of specific files. From 1.7.3 onwards, proper support for DLC and updates was included in Cemu.

Use the same process as above to download updates. Once decrypted, simply copy and paste these over the original game's files.

To install updates and DLC on Cemu (1.7.3+):

  • Run the game at least once.
  • Check Cemu's log.txt file and look for a line that says "Mounting local storage (AOC): .\mlc01\usr\title\NUMBERS\NUMBERS\aoc\"
  • Add (create) folders with the same name as the above (substituting the "NUMBERS" bit with the actual numbers) in your "CemuFOLDER/mlc01/usr/title" folder.
  • Add any updates (which must be added first) you want to the "CemuFOLDER/mlc01/usr/title/NUMBERS/NUMBERS/" folder.
  • Create a folder named "aoc" and put the DLC files into there. The "code", "content", and "meta" folders of the actual game itself also go in the "aoc" folder.

Amiibo Support[edit]

Amiibo are hard-to-find figurines unlocking various on-disc content in select 3DS and Wii U games. They use the NFC technology. Nintendo Amiibo data is distributed online as NFC tags (.bin files). There's a regularly updated complete set of the official ones but there are also unofficial spoofed packs on various other sites.

Recent versions of Cemu include Amiibo support. Simply go to NFC / Scan NFC Tag from file, and load the relevant .bin file. Keep in mind Amiibo support in Cemu is incomplete right now and not all figurines are compatible yet - though incompatibilities may be caused by bad Amiibo dumps as well.

Setting Up Cemu[edit]

Controls[edit]

Cemu added native support for Wii Remote controllers as of 1.12.0.

Cemu cannot connect to a real (or emulated) 3DS.

Cemuhook[edit]

Using this is completely optional.

Download the latest version compatible with your Cemu version, unpack it to the same directory as cemu.exe and right-click on dbghelp.dll, check Proprieties, Digital Signatures tab, select a signature and press Details. This should make it no longer crash at start-up. Make sure you also have the latest GPU driver installed, as well as both x86 and x64 versions of the Microsoft Visual C++ 2017 X64 Redistributable.

Whenever you boot Cemu now, this cemuhook tool is enabled by default and offers various additions for better motion control emulation or some graphical hacks that greatly enhance Zelda BOTW in particular. Accept to download the missing shared fonts as well as to make the text in some games (Super Mario Maker among others) display correctly.

Enabling "GX2SetGPUFenceSkip (HACK)" enhances graphical emulation in BOTW in particular. A pre-installed Graphical Pack that comes with recent versions of Cemuhook, "LWZX Crash Workaround", as well as the "GX2DrawDone()" option under Experimental, should help with some general crashes specific to BOTW.

Shader Caches[edit]

When your game is loaded, check for its ID on the title bar in front of "SaveDir:" and note it down. The directory where transferable shader caches are stored is .\Cemu\shaderCache\transferable. They're generated the first time you play through a game and at that time cause noticeable stuttering. You can download a complete cache from places like here and rename them to match your game version's ID to spare yourself most of that unpleasant experience. Just keep in mind that shader caches from versions older than 1.8.0 are incompatible with later versions of Cemu.

At startup, Cemu will prepare a compiled version of that cache under .\Cemu\shaderCache\precompiled and that one depends on your GPU driver, so you might want to erase it if any problems or crashes when compiling shaders at startup occur.

Troubleshooting/Speeding up[edit]

Shadercaches[edit]

Shaders are normally cached as you play the game. This can cause a lot of stutters and slow the game down.

Cemu accepts other shader caches that can be traded online. You can go to /r/Cemucaches and search for the ones you want. It's often very difficult to generate a complete cache for large games, and will not completely eliminate stuttering.

Some settings in the Nvidia control panel might help.

Some games' transferable caches may cause slowdowns on some graphics cards like the GeForce GTX 970. If this is the case, you will have to generate your own shaders and delete the ones you downloaded. In the case of the GeForce, also consider deleting the .bin and /toc file in your GLCache at %APPDATA%\NVIDIA\GLCache\(hexstring)\(hexstring).

Native H.264 Decoder[edit]

MP4 videos are often encoded for Wii U games with the expectation that the hardware plays it back on-the-fly, but because the x86 architecture is not PowerPC, this is resource-intensive for Cemu since it has to run the PowerPC video decoder. An unofficial utility called Cemuhook bypasses this by playing H.264 video directly from Windows codecs that are programmed for x86.

Disable Hyperthreading[edit]

Cemu may not be programmed well with hyperthreading. To disable it, go into the Task Manager, right-click cemu.exe and then set these affinities:

Processor affinity.png

Graphics Packs[edit]

To work around emulation bugs and other problems the way Dolphin does, "Graphic Packs" are title-specific property sheets which define advanced settings you might not be able to change in the interface. Basic rendering options including shadow resolution and quality, post-processing effects like bloom, lighting and god rays, custom anti-aliasing, and such can be applied here. You can even use them to reduce the internal resolution for an increase in the framerate. This is not to be confused with Texture Packs, which are replacement textures; Cemu doesn't support that, but it is planned.

The "Graphic Packs" themselves are folders under the graphicPacks directory. They can be named anything, but they should contain the "rules.txt" file. A bare-bones example of a "Graphics Pack", called "Bayo_1080p", would look like this:

[Definition]
titleIds = 0005000010172600,0005000010172700,000500001011b900,000500001014db00,0005000010157e00,0005000010157f00
name = "Bayonetta 1 + 2 - 1080p"

[TextureRedefine]
width = 1280
height = 720
overwriteWidth = 1920
overwriteHeight = 1080

Whenever the titleId matches the current one, Cemu will show the Graphics Pack under Options -> Graphics Pack. If you don't know what the titleId of the game you want is, check the logs.txt file. You can safely delete it in the event that it gets too big for a text editor to parse.

The overwriteWidth and overwriteHeight properties used in this example will upscale the game from 720p to 1080p. But if the game doesn't have all of its textures in the specified resolution, they won't be upscaled and could look messy as a result. In this case, this problem is seen in some FMVs in the game. This is the purpose of the TextureRedefine rule.

See some of the community graphics packs at this page.

Issues[edit]

  • Save states aren't getting implemented any time soon. This has a lot to do with the complexity of the Wii U memory layout and architecture, as well as the huge file size. As a result, the current developers are not interested in implementing them.
  • The emulator is still unfinished and unoptimized, as noted in the lack of efficient and stable H.264 video decoding, causing glitchy videos. This is worked around with Cemuhook entirely, but its approach to video decoding is unlikely to be taken into the emulator.

Piracy[edit]

There are anti-piracy measures on the Patreon early-access builds that are put behind the $5 tier. Backers putting out these builds can get banned if they're caught, and when the program fails verification, it locks down some features that impact performance.

Until 1.7.5 was released, mudlord put out cracked versions of early builds on his personal blog. A subreddit and Discord server was made to discuss Cemu piracy.

The official subreddit for Cemu advises against downloading unofficial "builds", saying they could potentially be traced with malware, and have made it one of their rules not to advocate it. The Cemu piracy subreddit has encountered malware authors taking advantage of this.

External links[edit]