Counter-Strike: Global Offensive

Counter-Strike: Global Offensive is an old game by modern standards, and this pairing—a six-core Intel Core i5-9400 with the flagship NVIDIA GeForce RTX 4090—creates a fascinating bottleneck scenario. The data shows that even at 4K Ultra, this combo never drops below 300 FPS, which means the RTX 4090 is essentially idle most of the time. The real story here is how the CPU and GPU trade places as the limiting factor depending on resolution and settings, and what that means for someone trying to get the highest possible framerates in a competitive shooter.

Resolution Scaling

The measured FPS data reveals a clear pattern: resolution scaling has a dramatic effect, but only at the higher settings. At Low settings, the frame rate drops from 870.7 FPS at 1080p to 517.5 FPS at 4K—a 40.6% reduction. At Ultra settings, the drop is steeper in relative terms: 743.1 FPS at 1080p falls to 323.1 FPS at 4K, a 56.5% reduction. This tells you that the RTX 4090 is finally being taxed at 4K Ultra, while at 1080p Low, the i5-9400 is the ceiling.

The transition from 1440p to 4K is where the GPU starts to matter more. At High settings, 1440p produces 641.5 FPS, which drops to 377 FPS at 4K—that is a 41.2% hit. Compare that to the 1080p-to-1440p gap at High settings: 783.9 FPS down to 641.5 FPS, a smaller 18.2% decline. This non-linear scaling indicates that the game becomes increasingly GPU-bound as pixel count rises, but it remains heavily CPU-bound at 1080p across all settings. The fact that 1080p Low (870.7 FPS) is only 17.2% faster than 1080p Ultra (743.1 FPS) confirms that resolution, not quality settings, is the primary lever for FPS gains at this pairing.

GPU Role

The RTX 4090's specifications are almost absurdly overkill for CS:GO, but the data shows exactly where that hardware does and doesn't matter. With 24 GB of GDDR6X memory on a 384-bit bus delivering 1.01 TB/s of bandwidth, the card is never remotely close to a memory capacity limit in this game. The 16384 shading units and 512 TMUs are equally underutilized; the measured frame rates at 1080p are far more dependent on the CPU's 2.90 GHz base clock boosting to 4.10 GHz.

The GPU's boost clock of 2520 MHz and base clock of 2235 MHz are relevant only at 4K Ultra, where the card is actually doing work. At that setting, the 4090's 82.58 TFLOPS of FP32 performance and 443.5 GPixel/s pixel rate are what push the game to 323.1 FPS. At lower resolutions and settings, the card is effectively cruising, and its 450 W TDP is mostly theoretical headroom. The 4090's 91st percentile ranking among all GPUs and its average benchmark score of 66473 tell you this is a top-tier part, but CS:GO is not the workload that flatters it.

The GPU's memory clock of 1313 MHz (21 Gbps effective) and 128 RT cores are features that CS:GO simply does not exercise. This is a DirectX 9-era game at its core, and the 4090's support for DirectX 12 Ultimate, OpenGL 4.6, and Vulkan 1.4 is irrelevant here. What matters is that at 4K Ultra, the 4090's raw rasterization power—its 176 ROPs and 1,290.2 GTexel/s texture rate—is finally the limiting factor, producing 377 FPS at High and 323.1 FPS at Ultra.

Settings Recommendations

The measured rows make the optimal settings choice unambiguous for competitive play. At 1080p, the difference between Low and Ultra is only 127.6 FPS (870.7 vs 743.1), which is a 14.7% penalty for maxed-out visuals. Given that CS:GO is a game where visibility and framerate matter more than graphical fidelity, Low settings at 1080p are the best choice for pure performance. The 870.7 FPS result is the highest measured value in the entire dataset.

For players who want better visuals without sacrificing too much, Medium at 1440p is the sweet spot. The data shows 727.4 FPS at 1440p Medium, which is only 16.5% lower than the absolute peak at 1080p Low. This is a better trade than 4K High, which delivers 377 FPS—less than half the peak—and requires the GPU to work much harder. At 4K, Ultra is strictly worse than High, with a 14.3% FPS penalty (323.1 vs 377), so there is no reason to use Ultra at that resolution unless you are chasing eye candy over frame rate.

The data also suggests that High settings at 1080p (783.9 FPS) are a reasonable compromise if you want better shadows and textures, since the gap to Low is just 10%. However, the jump from High to Ultra at 1080p costs 40.8 FPS (783.9 to 743.1), so Ultra is the least efficient preset across all resolutions. For a 144Hz or 240Hz monitor, any setting below 4K will exceed the display's refresh rate, making settings purely a visual preference rather than a performance decision.

How This Combo Ranks

This specific combo ranks 138th out of 1605 tested combinations in CS:GO, placing it in the top 8.6% of all pairings. That ranking might seem low for a combo containing the RTX 4090, but it reflects the i5-9400's limitations. The CPU has a 50th percentile ranking among all CPUs, meaning half of all processors tested were faster. Its average benchmark score of 2305 puts it within 0.6% of the Intel Core i7-8809G and 0.2% of the Intel Core i3-10305, which are its closest rivals.

The GPU, by contrast, ranks in the 91st percentile, and its nearest rivals—the NVIDIA Tesla T4, Tesla P40, AMD Radeon Pro Vega 56, and Quadro P6000—are all within 1.3% of its average score. The mismatch between a 91st-percentile GPU and a 50th-percentile CPU is what caps this combo at 138th place. In CS:GO, which is notoriously CPU-bound, the i5-9400's six cores and six threads are the weak link. The 138th rank means there are 137 combinations that deliver higher average FPS, almost certainly those with faster CPUs paired with mid-range GPUs.

The practical takeaway is that this combo is overkill for the GPU and underpowered on the CPU side. If the goal is maximum FPS in CS:GO, the data suggests that a stronger CPU with a weaker GPU would rank higher. But if you already own this combo, the 4K results show it is still exceptionally capable, just not the optimal use of the RTX 4090's potential.

FAQ

Q: Is the RTX 4090 the bottleneck at 1080p Low settings?

A: No. At 1080p Low, the combo achieves 870.7 FPS, which is the highest measured value. The i5-9400's six cores are the limiting factor, as evidenced by the fact that upgrading the GPU would not improve this number.

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

A: 1440p Medium offers the best balance, delivering 727.4 FPS while allowing the GPU to do more work than at 1080p. This is only 16.5% below the peak 1080p Low result and provides better image quality.

Q: How much FPS does Ultra settings cost compared to Low?

A: At 1080p, Ultra is 127.6 FPS slower than Low (743.1 vs 870.7). At 4K, the penalty grows to 194.4 FPS (323.1 vs 517.5), showing that Ultra becomes increasingly expensive at higher resolutions.

Q: Can this combo handle a 360Hz monitor?

A: Only at 1080p Low (870.7 FPS) or 1080p High (783.9 FPS). At 1440p, only Low (772.8 FPS) and Medium (727.4 FPS) exceed 360 FPS. At 4K, no setting reaches 360 FPS; the best is Low at 517.5 FPS, which is still above 360.

Q: Why does the combo rank only 138th despite having an RTX 4090?

A: The i5-9400 ranks in the 50th percentile among CPUs, while the RTX 4090 ranks in the 91st percentile. CS:GO is CPU-bound, so the processor holds back the GPU, capping the combo's ranking at 138th out of 1605.

Q: Is there any setting where the GPU is clearly the bottleneck?

A: Yes, at 4K Ultra (323.1 FPS) and 4K High (377 FPS). The large FPS drops from 1440p to 4K at these settings indicate the RTX 4090 is finally being fully utilized.

Measured FPS Breakdown

At 1920x1080, the combo delivers its highest frame rates. Low settings produce 870.7 FPS, Medium 826.8 FPS, High 783.9 FPS, and Ultra 743.1 FPS. The spread from Low to Ultra is 127.6 FPS, with each step from Low to Medium costing 43.9 FPS, Medium to High costing 42.9 FPS, and High to Ultra costing 40.8 FPS.

At 2560x1440, the numbers drop but remain extremely high. Low settings hit 772.8 FPS, Medium 727.4 FPS, High 641.5 FPS, and Ultra 545.6 FPS. The gap between Low and Ultra widens to 227.2 FPS, showing that the GPU is starting to matter more. The step from Medium to High is the largest penalty at 85.9 FPS.

At 3840x2160, the GPU finally becomes the primary factor. Low settings still manage 517.5 FPS, Medium 436.6 FPS, High 377 FPS, and Ultra 323.1 FPS. The total spread from Low to Ultra is 194.4 FPS, and every settings step costs between 40.9 and 81.4 FPS. The largest single drop is from Medium to High at 59.6 FPS, indicating that High settings at 4K are where the RTX 4090's pixel rate and memory bandwidth start to show their limits.