Doom

The pairing of the Intel Core i5-9400 with the NVIDIA GeForce RTX 5090 D in Doom produces a dataset that is far more revealing about the CPU's limitations than the GPU's immense capabilities. The measured frame rates show a system that is heavily constrained by processor performance at lower resolutions, while the GPU only begins to stretch its legs at 4K. This is a classic case of a generational mismatch, where a 2018 six-core processor acts as a bottleneck to a flagship 2025 graphics card, resulting in a performance profile that is inverted from what the hardware specifications alone would suggest.

Resolution Scaling

The most striking observation in the data is the surprisingly shallow frame rate scaling as resolution increases. From 1080p to 1440p, the average FPS drop is minimal across all settings, and the jump to 4K, while more significant, does not represent the dramatic performance cliff typically seen when a GPU becomes fully saturated. At High settings, the average frame rate only falls from 228 FPS at 1920x1080 to 197 FPS at 2560x1440, a modest reduction. The more telling drop occurs when moving from 1440p to 4K, where the average falls to 125 FPS. This pattern indicates that at 1080p and 1440p, the rendering pipeline is being throttled by the CPU, which cannot feed the RTX 5090 D enough data to reach its full potential.

The scaling from Low to Ultra settings reinforces this diagnosis. At 1080p, the difference between Low and Ultra is only 42 FPS (254 down to 212), which is a relatively small margin for a game like Doom. This suggests that even at the highest settings, the GPU has spare capacity that the CPU cannot utilize. The situation changes dramatically at 4K, where the performance gap between Low (170 FPS) and Ultra (102 FPS) expands significantly. This 68 FPS spread at 4K, compared to the 42 FPS spread at 1080p, demonstrates that the GPU is finally becoming the primary limiting factor at the highest resolution, as the increased pixel workload begins to outweigh the CPU's instruction-feeding bottleneck.

The data shows that the system is CPU-bound for the majority of the tested configurations. The transition to a GPU-bound state only occurs at the 3840x2160 resolution, where the sheer number of pixels demands more from the RTX 5090 D's 32 GB of memory and 512-bit bus. The 4K results, while still high in absolute terms, show the kind of resolution-based scaling that one would expect from a balanced system. The fact that the 1440p results are so close to the 1080p results is the clearest indicator that the Intel Core i5-9400 is holding the system back, preventing the user from experiencing the full benefit of the high-refresh-rate potential of the lower resolutions.

GPU Role

The NVIDIA GeForce RTX 5090 D is a behemoth of a graphics card, built on the Blackwell 2.0 architecture with a 5 nm process. Its specifications are staggering, including 32 GB of GDDR7 memory on a 512-bit bus, yielding a bandwidth of 1.79 TB/s. The card's compute capabilities are equally impressive, with an FP32 throughput of 104.8 TFLOPS and a pixel rate of 423.6 GPixel/s. However, in this specific pairing, the data suggests that these massive resources are largely underutilized until the resolution is pushed to 4K.

The GPU's role in this benchmark is primarily defined by its ability to maintain high frame rates when the CPU is not the bottleneck. At 1080p and 1440p, the RTX 5090 D is essentially waiting for the processor. The high memory bandwidth and large frame buffer are irrelevant when the CPU is struggling to process game logic and issue draw calls. The card's impressive 2407 MHz boost clock and 176 ROPs are not the limiting factors at these resolutions; the 6-core, 6-thread processor is.

It is only at 3840x2160 that the GPU's architecture begins to show its worth. The 4K Medium preset, with an average of 148 FPS and a minimum of 126 FPS, demonstrates that the card can handle a substantial workload while maintaining playable frame rates. The 4K Ultra preset, which drops to an average of 102 FPS, shows the first signs of the GPU being pushed, though it still delivers a smooth experience. The performance data indicates that the RTX 5090 D is more than capable of handling this title, but its full potential is masked by the CPU. The GPU's percentile ranking of 92 among all GPUs and its average benchmark score of 77712 are not reflected in the 1080p or 1440p numbers, which are held back by the processor.

Settings Recommendations

Given the CPU bottleneck observed at 1080p and 1440p, the choice of graphics settings has a diminished impact on performance at these resolutions. The data shows that the user can effectively run the game at Ultra settings without a significant performance penalty compared to Low. At 1920x1080, the difference between Ultra (212 FPS) and High (228 FPS) is only 16 FPS, and the jump from Medium (242 FPS) to Low (254 FPS) is similarly small. This suggests that for users with a high-refresh-rate 1080p or 1440p monitor, the optimal strategy is to maximize visual quality, as the CPU is the limiting factor, not the GPU.

The recommendation changes at 4K, where the GPU becomes the primary constraint. At 3840x2160, the High preset offers a substantial improvement over Ultra, with an average of 125 FPS compared to 102 FPS. This 23 FPS gain is significant and makes the High preset the best choice for a balanced experience at this resolution. The Medium preset at 4K, with an average of 148 FPS, is even better for performance, but the visual fidelity trade-off may not be worth it for all users. The data suggests that for a 4K display, High settings provide the best combination of visual quality and frame rate, ensuring a smooth and responsive experience without overburdening the GPU unnecessarily.

In summary, the measured rows indicate that the "best" experience is dependent on the target resolution. For 1080p and 1440p, Ultra settings are effectively free in terms of performance and should be used to get the most out of the game's visuals. For 4K, High settings are the sweet spot, offering a significant performance boost over Ultra while maintaining a high level of graphical fidelity. The Low preset is only useful for those seeking absolute maximum frame rates, but it sacrifices too much visual quality for a marginal performance gain in this CPU-limited scenario.

How This Combo Ranks

The combination of the Intel Core i5-9400 and the NVIDIA GeForce RTX 5090 D ranks 419 out of 2930 tested combos in Doom. This places it in the top 14.3% of all configurations, which is a strong showing overall. However, this ranking is likely a reflection of the sheer power of the GPU, which can brute-force high frame rates even when paired with a less capable processor. The rank reflects the RTX 5090 D's ability to deliver playable performance, but it does not tell the whole story of the system's inefficiency.

The ranking is lower than what one might expect from a GPU that sits in the 92nd percentile of all GPUs and has a nearest rival in the AMD Radeon RX 6850M XT, which it outperforms by 1.1% in average benchmark score. The high combo rank is dragged down by the CPU, which only sits in the 47th percentile of all CPUs. The Intel Core i5-9400's average benchmark score of 2254 places it in close competition with the Intel Core i7-1068NG7, which is only 0.2% behind. This indicates that the processor is a mid-range part, and its pairing with a flagship GPU creates a bottleneck that prevents the system from achieving a top-tier ranking. The data suggests that the combo's rank is a direct result of the GPU's raw power compensating for the CPU's shortcomings, rather than a sign of a balanced and optimized system.

CPU Role

The Intel Core i5-9400 is a Coffee Lake processor with 6 cores and 6 threads, a base clock of 2.90 GHz, and a boost clock of 4.10 GHz. Its specifications, including a 9 MB shared L3 cache and support for dual-channel DDR4 memory, are typical for a mid-range desktop processor from 2018. However, in the context of this benchmark, its role is clearly that of a limiting factor. The processor's 47th percentile ranking and its average benchmark score of 2254, which is nearly identical to the Intel Core i7-10710U (0.3% faster), highlight its mid-range status.

The benchmark results from the FPS data paint a clear picture of CPU limitation. The fact that 1080p and 1440p frame rates are so similar indicates that the processor cannot deliver frames fast enough to take advantage of the lower resolution's reduced pixel workload. The CPU's 6 threads are likely being fully utilized, and its 14 nm process node and 65 W TDP are not indicative of a processor designed for high-end gaming alongside a top-tier GPU. The data shows that the CPU is the primary constraint in this system, and its performance is the reason why the RTX 5090 D does not achieve the frame rates it is capable of at lower resolutions.

The CPU's role becomes less critical at 4K, where the GPU's workload increases. At this resolution, the processor is able to keep up with the GPU's demands, and the system's performance is more balanced. The 4K results show a more typical scaling pattern, with the GPU becoming the bottleneck. This suggests that the Intel Core i5-9400 is only a sufficient match for the RTX 5090 D when the resolution is high enough to offload a significant portion of the work onto the graphics card. In titles or scenarios that are less GPU-intensive, this CPU would likely be a severe bottleneck, preventing the user from fully utilizing the graphics card's potential.

Measured FPS Breakdown

The measured FPS data provides a detailed look at the system's performance across three resolutions and four settings presets. At 1920x1080, the system achieves its highest frame rates, with an average of 254 FPS on Low settings. The Medium preset averages 242 FPS, with a minimum of 205 FPS and a maximum of 278 FPS. High settings drop the average to 228 FPS, while Ultra settings bring it down to 212 FPS. These numbers are all exceptionally high and would provide a very smooth experience on any monitor, but the small spread between presets confirms that the CPU is the limiting factor.

At 2560x1440, the performance is still very high, with the Low preset averaging 219 FPS. The Medium preset averages 209 FPS, with a minimum of 178 FPS and a maximum of 240 FPS. High settings see a drop to 197 FPS, and Ultra settings average 183 FPS. The scaling from 1080p to 1440p is minimal, with a maximum drop of only 35 FPS between the Low presets. This reinforces the CPU bottleneck theory, as the GPU is not being taxed enough by the increased resolution to cause a significant performance hit.

The 3840x2160 results show the most significant performance scaling. The Low preset averages 170 FPS, which is a substantial drop from the 1440p Low preset. The Medium preset averages 148 FPS, with a minimum of 126 FPS and a maximum of 170 FPS. High settings average 125 FPS, and the Ultra preset brings the average down to 102 FPS. This resolution demonstrates a much clearer separation between settings, indicating that the GPU is now the primary bottleneck. The 4K data shows that the system can still deliver playable frame rates at the highest resolution, but the performance is more sensitive to graphical settings, making the High preset the recommended choice for a balanced 4K experience.