Description:
After updating to SU4, enabling FSR3 Frame Generation ×2 on triple 4K monitors causes severe stuttering despite high FPS and no spikes.
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Average FPS remained high (~60–80) when FSR3 ×2 was enabled.
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Center and side monitors experience severe frame pacing issues, making the sim effectively unplayable.
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Disabling FSR3 removes the stutter but eliminates frame generation benefits.
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In SU3, FSR3 ×2 ran smoothly across all three monitors with similar FPS.
Steps to Reproduce:
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Configure three 4K monitors , DLSS or TAA
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Launch MSFS 2024 SU4.
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Enable FSR3 Frame Generation ×2 globally.
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Observe severe stuttering and micro-hitches, despite FPS averaging 60–70.
Expected Behavior:
- FSR3 ×2 should function across all three monitors, providing smooth frame rates and stable frame pacing as in SU3.
Actual Behavior:
- Triple-monitor FSR3 ×2 produces severe stutter despite high FPS.
System Specs:
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GPU: NVIDIA RTX 4090
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CPU: AMD Ryzen 9 9800X3D
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RAM: 64 GB DDR5-6000
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Monitors: 3× 4K
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SU4 Release
Performance Metrics (triple 4K, FSR3 ×2 enabled):
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Main thread: 6 ms
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Render thread: 10–12 ms
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GPU: 16–17 ms
Severity: High — triple-monitor FSR3 ×2 is unplayable at high visual fidelity despite high FPS.
Suggested Investigation:
- Restore proper FSR3 multi-monitor scheduling as in SU3.
DETAILED REPORT
Detailed Report. SU4 Performance Regression on Triple 4K (9800X3D + 4090)
System Specs:
- CPU: Ryzen 9 9800X3D
- GPU: RTX 4090
- Motherboard: X870E
- RAM: 64GB DDR5‑6000
- Displays: Triple 4K TVs
Steps to Reproduce
- Launch MSFS 2024 SU4 on a triple‑4K setup.
- Set Anti‑Aliasing = DLSS Quality.
- Enable FSR3 Frame Generation.
- Run with dynamic target = 60fps baseline (no FPS lock).
- Fly in moderately dense areas (e.g., Washington DC, New York, London).
- Observe native FPS swings and thread frametime graphs.
Expected Behavior (SU3 Baseline)
- Terrain LOD stable at 100 minimum, often scaled to 200–300 without issue.
- Objects LOD stable at 150 baseline, often higher.
- Native FPS held close to 60 baseline target, with swings manageable.
- Frame pacing smooth across triple screens, only occasional stutters in extreme density (Tokyo, Manhattan).
- DLSS Quality + FSR FG produced consistent results, with FG doubling perceived FPS smoothly.
Actual Behavior (SU4 Regression)
- Main + render thread pacing jitter introduced, visible across all scenarios.
- Running unlocked with a dynamic 60fps target produces constant stutters and large picture jumps, even in moderately dense areas.
- Terrain LOD above 150–180 and Objects LOD above 120–150 exacerbate the issue.
- Native FPS swings between 45–70, FG doubles to 90–140 perceived, but pacing is unstable and immersion breaks.
- The simulator is unflyable in this state — stutters are constant and severe.
- The only way to achieve tolerable smoothness is to lock FPS at 30 with FG enabled while using TAA, eliminating swings but sacrificing responsiveness, fluidity and higher TLOD values regularly.
Impact
- SU3 allowed high LOD values and smooth triple‑screen immersion at a dynamic 60fps baseline, with only occasional stutters in extreme density.
- SU4 forces users into rescued settings everywhere, with degraded clarity and immersion.
- Frame Generation (FSR/DLSS) masks some stutter but cannot overcome the underlying thread pacing issues.
- Overall experience is unflyable bad and constantly stuttering, even on top‑end hardware.
Key Point for Developers
SU4 introduced a main‑thread pacing regression that makes previously stable LOD values unusable on triple‑screen setups. Running unlocked at a dynamic 60fps baseline now produces constant stutters and large picture jumps, forcing users to lock at 30fps with FG to maintain playability. This is a clear regression from SU3, where dynamic 60fps was smooth and stable across most environments
