How to Enable Nvidia SLI on Ubuntu for Optimal Gaming Performance.
By default, Ubuntu will use the open-source video driver Nouveau for your NVIDIA graphics card. This driver lacks support for 3D acceleration and may not work with the very latest video cards or technologies from NVIDIA.
Current limitations on Nvidia’s drivers are as follows:
- Linux only supports SLI & Multi-GPU (Two-GPUs-on-one cards such as the GTX 690) can be enabled, but only via command prompts in the Terminal.
- Only works on desktop platforms, SLI on mobile GPUs is unsupported.
- Only ID Tech 4 Engine games are officially supported in SLI by creating an “Application Profile” with GLDoom3 set to “true”. Games on ID Tech 4 engine include Quake 4, Enemy Territory: Quake Wars, Doom 3, and Prey and Open Source games on ID Tech 4 include The Dark Mod.
- GPUs with ECC enabled may not be used in an SLI configuration.
- SLI on Quadro-based graphics cards always requires a video bridge.
- TwinView is also not supported with SLI or Multi-GPU. Only one display can be used when SLI or Multi-GPU is enabled, with the exception of Mosaic.
- If X is configured to use multiple screens and screen 0 has SLI or Multi-GPU enabled, the other screens configured to use the Nvidia driver will be disabled. Note that if SLI or Multi-GPU is enabled, the GPUs used by that configuration will be unavailable for single GPU rendering.
- Alternate Frame Rendering (AFR) and Split Frame Rendering (SFR) are supported in Linux. AFR2 is not supported nor is it planned for Linux.
Alternate Frame Rendering (AFR) is supported. This SLI mode uses each card to render one frame then the next card renders the following. For example, in two-way AFR, GPU1 renders frames 1, 3, 5, etc. and GPU2 renders 2, 4, 6, etc. Outside of the ID Tech 4 engine Alternate Frame Rendering does not work on any card other than the first which causes framerates to drop by 50%. This is a known bug and nVidia is currently working on this issue.
SLI Profiles are NOT included with the drivers, unlike the Windows version of the nVidia drivers. They must be manually created for ID Tech 4 Engine-based games. To learn how to make them yourself, please read the Creating Application Profiles section of this wiki page.
Split Frame Rendering (SFR) is also supported. This mode uses the first GPU to render the top half of the screen, and the second GPU to render the bottom half. This mode also does not function correctly outside of ID Tech 4. It will still render the full screen, but only at the speed of a single GPU.
Alternate Frame Rendering mode 2 (AFR2) is NOT supported in Linux. This mode is the opposite of Alternate Frame rendering by instead using the last GPU as the primary and every GPU above it as the next in line. For example, in three-way AFR2? GPU3 renders frames 1, 4, 7, etc. GPU2 renders frames 2, 5, 8, etc. and GPU1 renders frames 3, 6, 9, etc. In Windows, AFR2 is the preferred SLI mode as it tends to yield higher performance than AFR. My theory is because GPU1 is the primary card for video out, it uses a different GPU for the primary calculations it better balances the workload. I have not seen any documentation as to the specific reason AFR2 performs better.
Despite what was mentioned above, if you wish to try SLI here’s how to enable it via the terminal:
- Open up Terminal.
- Use the following command of your choice: sli=on (enables SLI) sli=auto (Allows nvidia-xconfig to automatically enable SLI if it detects an SLI-ready setup) sli=afr (enables SLI in AFR mode) sli=sfr (enables SLI in SFR mode).
Terminal commands:
sudo nvidia-xconfig -sli=on
sudo nvidia-xconfig -sli=auto
sudo nvidia-xconfig -sli=afr
sudo nvidia-xconfig -sli=sfr
sudo nvidia-xconfig -sli=off- Put in your password
- Reboot Ubuntu (sudo reboot via terminal or via the GUI)
- Open up the “nVidia X Server Settings” program
- Select any GPU in the list, and look for the screen output. If SLI is indeed enabled? It will say “(SLI)” at the end of the detected screen output.
The only difference is if you have a Multi-GPU (such as the GTX 690) you change the argument of sli to multiple. Terminal commands:
sudo nvidia-xconfig -multigpu=on
sudo nvidia-xconfig -multigpu=auto
sudo nvidia-xconfig -multigpu=afr
sudo nvidia-xconfig -multigpu=sfr
sudo nvidia-xconfig -multigpu=offIf you have Multi-GPU cards in your system in SLI (such as two GTX 690s with the appropriate SLI bridge) you just have to mix the commands together. Terminal commands:
sudo nvidia-xconfig -sli=on -multigpu=on
sudo nvidia-xconfig -sli=auto -multigpu=auto
sudo nvidia-xconfig -sli=afr -multigpu=afr
sudo nvidia-xconfig -sli=sfr -multigpu=sfr
sudo nvidia-xconfig -sli=off -multigpu=offOn Practice:
sudo nvidia-xconfig --sli=On- Reboot
NOTE: If you change the card or video card driver – you must repeat SLI configuration.
