To ensure that each GPU is contributing to the overall graphics performance in an optimal manner, the ForceWare drivers communicate with the graphics hardware to provide real-time load balancing during Split Frame Rendering (SFR). Checking the "Show GPU load balancing" option provides a visual representation of dynamic load balancing as it occurs.
With Alternate Frame Rendering (AFR, AFR2), frames are rendered by each GPU in an alternating fashion and is the preferred SLI mode since it typically has less communications overhead and better vertex-load balancing than SFR. AFR activity is depicted in the screenshot below as the vertical green bar on the left will rise and fall in both directions as performance scales. The middle horizontal line remains stationary in AFR and AFR2.
Load Balancing - Alternate Frame Rendering
Split Frame Rendering (SRF) activity is depicted in the opposite manner from AFR as the green horizontal line moves up and down the screen to indicate activity, while the vertical green bar on the left remains stationary. With SFR, one GPU is responsible for rendering the frames above the line, while the other GPU renders the frame below the line.
Load Balancing - Split Frame Rendering
NVIDIA's Display Property User's Guide contains a wealth of information and is updated for major driver releases. The Release 75 guide contains 209 that cover driver enhancements, system requirements, control panel features, nView multi-display features, configuring output (analog and digital displays, TV, and HDTV), driver settings, setup wizards and the history of driver features.
Display Property User's Guide Cover Page
A link to the Display Property User's Guide, along with the equally important Driver Release Notes and nView User's Guide, are always present near the bottom of the driver download page.
User Guide Links
With each major driver release, experienced users should read the enhancements section in the Display Property User's Guide. For drivers that are released within a major release, the relevant sections in the Driver Release Notes should be read.
The Driver Release Notes contain sections about issues that were resolved, open issues that have yet to be resolved, and product limitations. It is especially important to remain updated when new features, products, and technologies are released by NVIDIA.
Application Profiles debuted in driver Release 55 and allowed the user to associate a collection of driver settings, such as antialiasing, with an application or game. When a game was executed, the settings defined in the application profile for that game would be used.
A global profile is always present and is used in the event that a profile for the application being executed does not exist. A key feature of the profile system is that the application profile is ALWAYS supposed to override the global profile.
Remember that SLI does not automatically increase the performance of every game. NVIDIA maintains a list of SLI optimized games and provides a pre-determined, read-only, SLI rendering mode in each of the games' application profile. Although application profiles can now be altered, it is best to leave the SLI rendering mode, for those applications with read-only SLI rendering modes, alone.
Predefined SLI Rendering Mode
By following this procedure, you will be able to add new SLI profiles in addition to being able to assign one of five SLI rendering modes in lieu of the default single-GPU and multi-GPU modes.
Custom SLI Rendering Modes
Having the capability to add new SLI profiles allows the various SLI modes to be tested on older games that are not listed as SLI optimized, or newly released demos, that will eventually be listed as SLI optimized.
Also noteworthy are certain recommendations that NVIDIA provides for SLI in their GPU Programming Guide. Key areas that are covered include CPU bottlenecks, frame rate caps, vsync, and programming techniques specific to Direct X and OpenGL.