Roblox

The Intel Core i5-9400 paired with the NVIDIA GeForce RTX 4090 produces a profoundly CPU-limited experience in Roblox, where the sheer graphical headroom of the flagship GPU is largely wasted. Across all tested resolutions and settings, the 6-core, 6-thread Coffee Lake processor acts as a hard ceiling, preventing the frame rates from scaling in a manner consistent with the GPU's capabilities. The data indicates that this combo ranks 244th out of 3711 tested combinations, placing it in the top 7% of all systems tested for this title, but the performance deltas between settings and resolutions reveal that the bottleneck is consistently on the CPU side.

Resolution Scaling

The frame rate progression from 1080p to 4K reveals a system that is entirely constrained by the processor. At 1920x1080 with High settings, the system delivers 514 FPS. Moving to 2560x1440 drops this to 382 FPS, a reduction of 132 FPS. At 4K (3840x2160), the average falls to 216 FPS, which is a further 166 FPS decline from the 1440p result. This scaling pattern—a 25% drop from 1080p to 1440p and a 58% drop from 1080p to 4K—shows that resolution does have a measurable impact, but the absolute values remain extraordinarily high even at 4K.

The more telling observation is that the performance delta between Low and Ultra settings at each resolution is relatively narrow compared to what a GPU-bound system would exhibit. At 1080p, the spread between Low (554 FPS) and Ultra (464 FPS) is only 90 FPS. At 4K, the spread between Low (268 FPS) and Ultra (175 FPS) is 93 FPS. This consistency in the settings gap across resolutions suggests that while pixel throughput does increase the workload on the RTX 4090, the processor's ability to feed the game's simulation logic is the dominant factor. The i5-9400's 2.90 GHz base and 4.10 GHz boost clocks are simply not sufficient to keep a 16384-shading-unit GPU saturated in this lightly threaded physics and script-heavy title.

GPU Role

The NVIDIA GeForce RTX 4090's specifications are almost absurdly over-provisioned for Roblox, yet the data shows it still manages to push the frame rate to triple digits at every resolution. The GPU features 24 GB of GDDR6X memory on a 384-bit bus, yielding 1.01 TB/s of bandwidth and a 1.01 TB/s memory bandwidth figure. Its base clock of 2235 MHz and boost clock of 2520 MHz are high, but the actual limiter is not the GPU core. The 82.58 TFLOPS of FP32 compute and 443.5 GPixel/s pixel rate are far beyond what a sandbox game with blocky geometry typically demands.

The measured FPS data indicates that the RTX 4090 is barely breaking a sweat. Even at 3840x2160 Ultra, the average FPS is 175, which is still nearly three times the refresh rate of a standard 60 Hz monitor. The GPU's role here is to ensure that no matter how complex a user-generated Roblox world becomes, with its draw calls and texture loads, the rendering pipeline never becomes the limiting factor. The PassMark G3D score of 38194 and the 3DMark Steel Nomad DX12 score of 9223 confirm the GPU's raw capability, but in this specific title, those resources are largely idle. The GPU's percentile rank of 88 versus all GPUs is irrelevant to the gameplay experience because the CPU is the gatekeeper.

CPU Role

The Intel Core i5-9400 is the clear bottleneck, and the benchmark data from the CPU itself explains why. With 6 cores and 6 threads, it lacks the multi-threading that modern titles often utilize, and its Cinebench R23 multi-core score of 6629 is modest by current standards. The single-core score of 935 in Cinebench R23 is particularly telling, as Roblox's core simulation loop typically relies heavily on single-threaded performance. The processor's Geekbench single-core score of 1389 and multi-core score of 5141 align with its 47th percentile ranking among all CPUs, indicating it is a mid-range part from 2018.

In this system, the CPU's 9 MB of shared L3 cache and 256 KB per-core L2 cache are sufficient for Roblox's modest data footprint, but the clock speeds cap out at 4.10 GHz. The result is that the CPU cannot issue draw calls and physics updates fast enough to keep the RTX 4090's 128 RT cores and 512 tensor cores occupied. Evidence of this is the 1080p Low result of 554 FPS versus the 1080p High result of 514 FPS—a mere 7% difference. If the GPU were the bottleneck, the difference would be far larger. The CPU's nearest rivals, such as the Intel Core i7-1068NG7 and the AMD Ryzen 5 PRO 1500, have similar average benchmark scores (2259 and 2246 respectively), but none of them would be able to unlock the RTX 4090's full potential in this scenario either.

Measured FPS Breakdown

The complete dataset provides a clear picture of performance across all twelve measured configurations.

At 1920x1080, the system is almost entirely CPU-bound. Low settings produce 554 FPS, while Medium yields 536 FPS with a minimum of 456 FPS and a maximum of 617 FPS. High settings produce 514 FPS, and Ultra drops to 464 FPS. The tight clustering of these numbers—a range of just 90 FPS—shows that the GPU is never stressed, and the frame rate is dictated by how fast the i5-9400 can process the game's logic.

Moving to 2560x1440, the GPU begins to take on slightly more work, but the CPU still dominates. Low settings average 474 FPS, Medium averages 432 FPS (min 367, max 496), High averages 382 FPS, and Ultra averages 310 FPS. The spread between Low and Ultra here is 164 FPS, which is wider than at 1080p, indicating that the increased pixel count is starting to engage the RTX 4090 more meaningfully. Yet, even the Ultra result of 310 FPS is far above the refresh rate of any common gaming monitor.

At 3840x2160, the GPU's workload is substantial enough to show a more pronounced settings scaling. Low settings average 268 FPS, Medium averages 244 FPS (min 208, max 281), High averages 216 FPS, and Ultra averages 175 FPS. The 93 FPS difference between Low and Ultra at 4K is nearly identical to the 90 FPS difference at 1080p, which is a curious artifact of the bottleneck. It suggests that the CPU's frame generation ceiling is around the 554 FPS mark (1080p Low) and the GPU's rendering floor at 4K Ultra is 175 FPS, but the system never approaches a state where the GPU is fully utilized. The minimum FPS values recorded at Medium settings (456 at 1080p, 367 at 1440p, 208 at 4K) show that even in the worst-case measured frames, the performance is still exceptionally smooth.

How This Combo Ranks

The combo rank of 244 out of 3711 tested systems places this configuration in the 93rd percentile of all tested combos for Roblox. This is a surprisingly high rank given the CPU bottleneck, which indicates that most other tested systems feature even weaker processors. The ranking reflects the fact that Roblox is not a demanding title, and even a modest 6-core CPU from 2018 can achieve outstanding frame rates when paired with the fastest consumer GPU on the market.

However, the rank also obscures the inefficiency of this pairing. The RTX 4090's average benchmark score of 60347 places it in the 88th percentile of all GPUs, and its nearest rivals are professional workstation cards like the AMD Radeon Pro W6600M and the AMD Radeon PRO V710. In a GPU-bound title, this combo would likely rank in the top 10. In Roblox, the rank of 244 is held back by the CPU's 47th percentile standing. The delta between the CPU's performance and the GPU's performance is the defining characteristic of this system. The i5-9400's Cinebench R20 multi-core score of 2784 and single-core score of 392 are roughly 35-40% lower than what a modern high-end CPU would achieve, and that gap directly translates to the frame rate ceiling observed in the measured data.

FAQ

Q: Why is the frame rate so high at 1080p Low (554 FPS) but only slightly lower at 1080p Ultra (464 FPS)?

A: The 90 FPS difference indicates that the game is CPU-bound. The Intel Core i5-9400 can only generate a certain number of frames per second, and changing the GPU settings from Low to Ultra does not significantly alter the CPU's workload. The RTX 4090 is capable of rendering far more frames, but it is waiting for the CPU to send it draw calls.

Q: Is the RTX 4090 being fully utilized in this game?

A: No. The data shows that at 4K Ultra, the system only achieves 175 FPS, which is low for a GPU with 24 GB of GDDR6X memory and an 82.58 TFLOPS compute rating. The GPU's percentile rank of 88 among all GPUs and its PassMark G3D score of 38194 are far higher than what the frame rates suggest, confirming that the processor is the limiting component.

Q: What is the best resolution to play this game with this combo?

A: According to the measured data, 2560x1440 at Medium settings provides an average of 432 FPS with a minimum of 367 FPS. This offers a high frame rate with a reasonable balance of visual quality. The 4K Medium setting (244 FPS) is also viable, but the 1440p result has a higher minimum frame rate, indicating better consistency.

Q: How does the CPU's single-core performance affect the results?

A: The i5-9400 has a Cinebench R23 single-core score of 935 and a Geekbench single-core score of 1389. Roblox relies heavily on single-threaded logic, so these scores are more relevant than the multi-core scores. The 4.10 GHz boost clock is the highest frequency available, and it is this limit that caps the frame rate in the 500 FPS range at 1080p.

Q: Does the 24 GB of VRAM on the RTX 4090 matter for Roblox?

A: The 24 GB of GDDR6X memory is unnecessary for Roblox, as the game's assets are not large enough to come close to filling it. The memory bandwidth of 1.01 TB/s is also far more than needed. The benchmark results show no indication that VRAM capacity is a factor in any of the measured FPS values.

Q: What settings give the highest minimum frame rate?

A: At 1080p Medium, the minimum FPS is 456. At 1440p Medium, the minimum is 367. At 4K Medium, the minimum is 208. The Medium preset consistently provides the highest minimum FPS among the settings with min/max data, suggesting it avoids the worst frame-time spikes.

Settings Recommendations

The measured data suggests that the Medium preset offers the most balanced experience across all resolutions. At 1920x1080, Medium yields 536 FPS average with a 456 FPS minimum, which is only 18 FPS lower than Low but 72 FPS higher than Ultra. The 617 FPS maximum at 1080p Medium also shows the system has headroom to spare. The primary benefit of Medium over Low is improved visual fidelity without sacrificing the high minimum frame rate.

At 2560x1440, Medium again proves to be the sweet spot. The 432 FPS average with a 367 FPS minimum is substantially higher than the 310 FPS average on Ultra. The 1440p Medium result is also more than double the refresh rate of the fastest common gaming monitors, making it the recommended resolution for players who want high detail without hitting the CPU ceiling. The 4K Medium setting (244 FPS average, 208 FPS minimum) is playable and smooth, but the 1440p Medium offers a nearly 90% higher average frame rate.

For players with high-refresh-rate displays, 1080p Low or Medium is the logical choice, as both exceed 500 FPS on average. However, the data shows that the difference between Low and Medium at 1080p is minimal (554 vs 536 FPS), so there is no reason to select Low unless the absolute maximum frame rate is the sole objective. The Ultra preset is the least recommended option, as it provides the lowest frame rates at every resolution without a proportional visual benefit in a game like Roblox, where the art style is inherently low-polygon. The system's performance is so high that any of the four presets will deliver a playable experience, but the Medium preset maximizes the minimum frame rate while keeping the average well above 200 FPS even at 4K.