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SLI and VAS (OOM) Issues - Current Situation

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Questions about these two topics keep popping up from time to time and, I believe, may be causing a degree of exasperation amongst those Moderators who are constantly having to correct our understanding of what may be happening.


So, I thought it might be helpful to summarise the current state of play by reproducing the relevant content of those relevant posts made recently by Adam Breed, Engineering Project Manager and Beau Hollis, Prepar3D Rendering System Lead.


SLI Issues


Adam Breed (10 January, 2017):

"We have been working with NVIDIA on SLI issues and believe it is a combination of an Prepar3D application side and NVIDIA driver side."


Beau Hollis (11 January, 2017):

"I have been personally working with NVIDIA on this, and am happy to report that great progress is being made. We've found and fixed the performance and UI flicking introduced in HF2. Thanks to Nvidia's help, we believe that we can also resolve the visual effects flicking issue in our application code. We understand that specific driver versions may conflict with other applications, so we plan to fix this in-app, if possible, to give our users more flexibility.


EDIT: We also resolved a related SLI issue in HF2 where p3d might hang at 100% during loading. All these issues are specific to alternate frame rendering (AFR). Overriding application settings to use another SLI mode such as SLI AA is one way users have been able to work around these issues without completely disabling SLI."


VAS Issues and OOMs


Beau Hollis (12 January, 2017):

"We spent a good deal of time looking into VAS usage. Some specific bugs were fixed a as result as Adam mentioned previously:

- Some 3rd-party gauges leaked memory when the panel window resized. That bug dated all the way back to P3Dv1/FSX. We fixed it thanks to a detailed reproduction sample provided by an add-on developer.

-Another reported issue related to slewing very fast around world in top down. This bug was introduced back in P3Dv2.


We don't know of any more specific memory bugs at this time. Our recommendation is that users tune their settings and add-on usage to keep within the current memory limits.


Any time we update the sim, memory usage patterns may vary, and some re-tuning may be required. New features may require memory to implement. For example, as of 3.4, scenery models can now use visibility scripts to be more dynamic. These scripts shouldn't take up much memory, but we can't be sure how a feature like this might interact with add-on content. If an aircraft model with tons of visibility scripts was placed as a scenery model, it's memory footprint might be higher. We understand that for some use-cases, an older version may work better, so we've posted links to past releases to give users the option to go back.


Finally, I'd like to respond to the feedback about memory usage in general. We understand the frustration with OOMs, which is why we worked hard to provide major memory improvements for v3.0. In the move from v2 to v3, many heavy add-on users saw VAS drop by hundreds of megs or more. Performance and memory optimization will remain a high priority for us as the platform evolves. Big changes are often too risky to attempt for a point release or hot fix, which is why our focus has been on addressing specific reproducible bugs."



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Bump...just to keep this visible for a few days.



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