Doom

The pairing of the Intel Core i5-9400 with the NVIDIA GeForce RTX 4090 presents a classic high-end GPU with a mid-range CPU bottleneck scenario, particularly at lower resolutions. The measured data for Doom shows a system that is capable of extremely high frame rates, but the scaling across resolutions reveals where the processor begins to limit the graphics card's potential. This analysis breaks down the measured performance to determine the optimal settings and the role each component plays.

Resolution Scaling

The frame rate progression from 1080p to 4K clearly illustrates the shifting balance of load between the CPU and GPU. At 1920x1080 with Low settings, the system achieves an average of 256.8 FPS. Moving to 2560x1440 at the same Low settings, the average only drops to 217.1 FPS, a reduction of roughly 15%. However, the jump to 3840x2160 at Low settings brings the average down to 156 FPS, a much steeper 28% drop from the 1440p figure. This pattern indicates that at 1080p, the Intel Core i5-9400 is the limiting factor; the RTX 4090 is being held back by the CPU's ability to feed it frames, so reducing resolution does not yield the massive FPS gains one would expect from such a powerful GPU.

The trend becomes more pronounced at higher graphical presets. At High settings, the average FPS goes from 225.8 at 1080p to 195.6 at 1440p, and finally to 116.2 at 4K. The drop from 1440p to 4K is a significant 41%, which is a much larger performance hit than the 15% drop seen at Low settings for the same resolution change. This demonstrates that as the preset increases, the GPU's workload becomes more demanding, and the RTX 4090 begins to become the primary bottleneck. The data suggests that at 4K with High settings, the system is finally allowing the GPU to stretch its legs, but the CPU still prevents it from reaching its full potential.

The performance gap between Low and Ultra presets also widens with resolution. At 1080p, the difference between Low (256.8 FPS) and Ultra (213.8 FPS) is about 43 FPS. At 4K, that difference grows to nearly 60 FPS (156 vs. 96.3). This is a direct consequence of the GPU being more heavily utilized at higher resolutions, making the graphical settings more impactful on the final frame rate. The benchmark results indicate that this combo is best suited for high-refresh-rate 1440p gaming, where the CPU can still keep up and the GPU has enough work to do. At 4K, the system is still very fast, but the CPU bottleneck is less of a factor, and the GPU's raw power is more decisive.

GPU Role

The NVIDIA GeForce RTX 4090 is a monstrous piece of hardware, and its specifications in the fact pack are staggering. It features 24 GB of GDDR6X memory on a 384-bit bus, providing a massive 1.01 TB/s of memory bandwidth. Its boost clock is listed at 2520 MHz, and it houses 16,384 shading units. These figures translate to an immense amount of raw compute power, which is reflected in its benchmark scores, such as a Passmark G3D score of 38194 and a Geekbench OpenCL score of 317684. In the context of Doom, the GPU's role is to render the game's fast-paced environments and effects at high resolution and detail.

The measured FPS data shows the RTX 4090's capability. Even at 4K with Ultra settings, the game runs at an average of 96.3 FPS, which is well above the 60 FPS target for smooth gameplay. The GPU’s performance at lower resolutions is also noteworthy, but it is constrained by the CPU. The fact that the FPS does not scale linearly with resolution suggests that the GPU is not the primary bottleneck at 1080p. The GPU's massive memory bandwidth and 24 GB of VRAM are more than sufficient for Doom, which is not a particularly VRAM-hungry title by modern standards. The GPU's 91st percentile ranking among all GPUs further underscores its high-end status, though its nearest rivals in the synthetic benchmark averages, such as the NVIDIA Tesla T4 and AMD Radeon Pro Vega 56, are not gaming-focused cards.

The RTX 4090's launch MSRP is 1,599 USD. The data shows that the GPU is capable of delivering playable frame rates at 4K with the highest settings, but the pairing with the i5-9400 means its full potential is only realized when the resolution is high enough to put significant load on the graphics card.

Settings Recommendations

Based on the measured FPS rows, the optimal settings for this combination depend heavily on the target resolution and refresh rate. For 1080p and 1440p, the data suggests that the CPU is the limiting factor, so increasing graphical settings has a relatively small impact on performance. For instance, at 1440p, moving from Low (217.1 FPS) to High (195.6 FPS) only costs about 21 FPS. This makes High settings a clear recommendation for 1440p, as it provides a substantial visual upgrade for a modest FPS loss. The Ultra preset at 1440p (171 FPS) is also a solid choice, as it still maintains a very high frame rate while offering the best image quality.

At 4K, the GPU becomes the primary bottleneck, and settings have a more pronounced effect. The High preset at 4K delivers 116.2 FPS, which is an excellent experience for a 4K display. The Medium preset (138.5 FPS) is also a good option for those who want to prioritize frame rate over absolute visual fidelity. The Ultra preset at 4K (96.3 FPS) is still very playable, but the drop from High is significant. For a 4K 120Hz display, High is the recommended preset. For a 4K 60Hz display, Ultra is a viable and visually impressive choice, as it stays well above the 60 FPS threshold.

The data shows that the Low preset is rarely the best choice. At 1080p, it provides a 256.8 FPS average, but sacrificing visual quality for an extra 30 FPS over the High preset is not a worthwhile trade-off. The sweet spot for this hardware combo is to use High or Ultra settings, as the CPU bottleneck at lower resolutions means you are leaving performance on the table without gaining the visual benefits of higher presets.

FAQ

Q: Can this system run Doom at 4K with maximum settings?

A: Yes. The measured data shows an average of 96.3 FPS at 3840x2160 with Ultra settings. This is comfortably above the 60 FPS standard for smooth 4K gameplay.

Q: Is the CPU or GPU the main bottleneck at 1080p?

A: The benchmark results indicate the CPU is the primary limiting factor at 1920x1080. The FPS difference between Low (256.8) and High (225.8) settings is only about 31 FPS, suggesting the graphics card is not being fully utilized.

Q: What is the best preset for a 1440p high-refresh-rate monitor?

A: The High preset at 2560x1440 offers an average of 195.6 FPS. This provides an excellent balance of visual quality and performance, easily supporting a 144Hz or 165Hz monitor. The Ultra preset (171 FPS) is also a strong contender if you prioritize image quality.

Q: How much faster is the RTX 4090 compared to its nearest rival in synthetic benchmarks?

A: The data shows the RTX 4090 has an average benchmark score of 66473. Its nearest rival, the NVIDIA Tesla T4, has an average score of 66733, which is 0.4% higher. The AMD Radeon Pro Vega 56 is 0.9% lower, and the NVIDIA Quadro P6000 is 1.3% lower. These are all very close in synthetic averages.

Q: Does the Ultra preset at 4K provide a better experience than High?

A: It depends on your preference. Ultra delivers 96.3 FPS, while High delivers 116.2 FPS. If you have a 4K 120Hz display, High is the better choice to get closer to the refresh rate cap. If you have a 60Hz display, Ultra is a great option for maximum fidelity.

Q: Is the i5-9400 a good match for the RTX 4090 in this game?

A: The data shows it is a limiting factor at 1080p, but the system still delivers over 200 FPS on all presets at that resolution. At 4K, the CPU is less of a bottleneck, and the GPU's power is more evident. It is a workable pairing, but the CPU prevents the GPU from showing its full strength at lower resolutions.

CPU Role

The Intel Core i5-9400 is a 6-core, 6-thread processor based on the Coffee Lake architecture. It has a base clock of 2.90 GHz and a boost clock of 4.10 GHz. Its 9 MB of shared L3 cache is a key resource for gaming. In synthetic benchmarks, it scores 7969 in Cinebench R23 multi-core and 1125 in single-core, placing it at the 50th percentile of all CPUs. Its average benchmark score of 2305 is nearly identical to its nearest rivals, such as the Intel Core i3-10305, which is only 0.2% faster.

In the context of Doom, the CPU's role is to handle game logic, physics, and draw calls. The measured FPS data shows that the i5-9400 is the limiting factor at 1080p. The fact that the FPS does not increase significantly when lowering the resolution from 1080p to 1440p (e.g., from 256.8 to 217.1 at Low settings) is a classic sign of a CPU bottleneck. The CPU is simply unable to prepare frames fast enough to keep the RTX 4090 busy. This is not a flaw in the CPU, but rather a reflection of the enormous performance gap between these two components.

The CPU's 6 threads are sufficient for Doom, which is not heavily multithreaded. However, the relatively low boost clock of 4.10 GHz limits its single-thread performance, which is critical for high-FPS gaming. The benchmark results indicate that while the system is very fast, the i5-9400 holds the RTX 4090 back from achieving its maximum possible frame rates at 1080p. At 4K, the GPU becomes the bottleneck, and the CPU's limitations are less apparent. The data confirms that this CPU is a capable gaming processor, but it is out of its depth when paired with a flagship GPU at lower resolutions.

Measured FPS Breakdown

The following data points are the exact measured averages from the fact pack for the Intel Core i5-9400 and NVIDIA GeForce RTX 4090 combination.

1920x1080:

• Low: 256.8 FPS
• Medium: 242.5 FPS
• High: 225.8 FPS
• Ultra: 213.8 FPS

2560x1440:

• Low: 217.1 FPS
• Medium: 211.3 FPS
• High: 195.6 FPS
• Ultra: 171 FPS

3840x2160:

• Low: 156 FPS
• Medium: 138.5 FPS
• High: 116.2 FPS
• Ultra: 96.3 FPS

The data shows a consistent performance hierarchy across all resolutions, with Low settings yielding the highest average FPS and Ultra yielding the lowest. The most striking observation is the diminishing returns of lowering the resolution at 1080p and 1440p. The jump from 1440p to 4K, however, shows a much larger performance hit, particularly at higher presets, confirming the GPU becomes the primary bottleneck at that resolution. The system ranks 289th out of 1681 tested combos for this game, placing it in the top 17% of all configurations. This is a high-performance pairing, but the data makes it clear that the CPU is the constraining factor in many scenarios.