Doom

Resolution Scaling — how FPS drops from 1080p to 4K and what it says about the limiting component

The measured frame rates for this Intel Core i5-9400 + AMD Radeon RX 6750 XT combination reveal a clear pattern of GPU-bound scaling as resolution climbs. At 1080p High settings, the combo produces 177.4 FPS average. Moving to 1440p High drops that to 115.6 FPS, a reduction of roughly 35%. Stepping up to 4K High yields 62 FPS — a 65% decline from the 1080p figure. This steep falloff across resolution tiers indicates the Radeon RX 6750 XT becomes the primary limiting factor as pixel count rises, while the six-core i5-9400 has enough headroom to keep feeding frames at lower resolutions.

The Low preset tells an even more revealing story. At 1080p Low, the system hits 238.6 FPS. At 1440p Low, it still manages 158.7 FPS. But at 4K Low, the average collapses to 85.2 FPS. The gap between 1080p and 1440p Low is 79.9 FPS, while the gap between 1440p and 4K Low is 73.5 FPS — nearly identical drops. This linear scaling suggests that even at the lowest settings, the GPU's raw throughput — not the CPU — is what constrains performance at higher resolutions. The RX 6750 XT's 432.0 GB/s memory bandwidth and 13.31 TFLOPS FP32 throughput are being fully utilized as resolution increases.

Ultra settings amplify this trend. The 1080p Ultra average of 143.4 FPS drops to 92.5 FPS at 1440p, then to 53.7 FPS at 4K. The percentage loss from 1440p to 4K Ultra is 42%, slightly steeper than the 38% loss from 1080p to 1440p Ultra. This accelerating degradation points to the GPU's 12 GB GDDR6 memory and 192-bit bus being saturated by the combination of high resolution and maxed-out quality settings. The data suggests that for 4K Ultra, this combo is right at the edge — 53.7 FPS is playable but leaves little margin.

Settings Recommendations — which preset gives the best experience per the measured rows

Comparing the four measured presets across all three resolutions, the Medium setting emerges as the sweet spot for most scenarios. At 1080p Medium, the combo delivers 209 FPS — only 29.6 FPS behind Low but 65.6 FPS ahead of Ultra. At 1440p Medium, the 137 FPS average is 51.7 FPS above Ultra and just 21.7 FPS below Low. Even at 4K, Medium's 72.6 FPS is 18.9 FPS above Ultra and only 12.6 FPS below Low. This consistent positioning makes Medium the most balanced choice: it preserves the visual enhancements of higher settings while keeping frame rates comfortably above refresh-rate thresholds on standard displays.

For competitive play at 1080p, Low is the obvious pick. The 238.6 FPS average exceeds 240 Hz refresh capabilities, and the jump from Medium to Low (29.6 FPS) is larger than the jump from High to Medium (31.6 FPS), suggesting diminishing returns from Low to Medium. At 1440p, High at 115.6 FPS is the recommended preset for quality-focused players — it stays well above 100 FPS while offering better visuals than Medium. The 22.6 FPS difference between High and Medium at 1440p is acceptable, but the 23.1 FPS difference between High and Ultra makes Ultra harder to justify.

At 4K, the choices narrow. High at 62 FPS is the only preset that clears the 60 FPS threshold, making it the default recommendation for 4K displays. Medium at 72.6 FPS offers a safer margin, though the visual step down may be noticeable. Ultra at 53.7 FPS is borderline — technically playable but below the 60 FPS target that most gamers prefer. The data indicates this combo can handle 4K, but only with settings compromises that trade visual fidelity for smoothness.

FAQ — 4-6 Q&A pairs answerable from FACT PACK data

Q: Can this combo run Doom at 4K with playable frame rates?

A: Yes, but only with settings adjustments. At 4K High, the average FPS is 62, which clears the 60 FPS playability bar. Medium at 4K delivers 72.6 FPS for extra headroom, while Ultra drops to 53.7 FPS — below the 60 FPS threshold.

Q: What is the best resolution for this pair if I want to maximize frame rate?

A: 1080p is the strongest resolution, with all presets exceeding 140 FPS. Low hits 238.6 FPS, Medium reaches 209 FPS, and even Ultra maintains 143.4 FPS. At 1440p, only Low (158.7 FPS) and Medium (137 FPS) stay above 120 FPS.

Q: How does the RX 6750 XT's memory configuration affect 4K performance?

A: The GPU has 12 GB of GDDR6 memory on a 192-bit bus with 432.0 GB/s bandwidth. The 4K Ultra score of 53.7 FPS suggests the memory subsystem is a limiting factor at maximum settings, as the bandwidth is strained by the higher pixel count.

Q: Is the i5-9400 holding back the GPU at 1080p?

A: The data does not indicate CPU bottlenecking. At 1080p Low, the combo reaches 238.6 FPS, and the pattern of scaling from Low to Ultra (238.6 down to 143.4 FPS) shows the GPU is the primary performance driver. The CPU's 4.10 GHz boost clock and 6 cores provide adequate throughput.

Q: What is the frame rate difference between High and Ultra at 1440p?

A: High averages 115.6 FPS, while Ultra averages 92.5 FPS — a difference of 23.1 FPS. This is a 20% performance cost for the visual upgrade from High to Ultra, which may not be worth it for players prioritizing smoothness.

Q: How does this combo rank among all tested configurations for Doom?

A: It ranks 839th out of 1681 tested combos, placing it in the upper half of all configurations tested for this game. This mid-pack positioning reflects the balance between the six-core CPU and the mid-range GPU.

How This Combo Ranks — use comboRankInGame vs other tested combos

The combo's rank of 839 out of 1681 tested configurations places it squarely in the middle of the distribution — the 50th percentile. This is a notable result given the individual components' percentiles: the i5-9400 sits at the 50th percentile among all CPUs, while the RX 6750 XT is at the 79th percentile among all GPUs. The gap between the CPU's middling rank and the GPU's above-average rank explains why the combo lands in the middle rather than higher: the processor is not leaving performance on the table, but it is also not boosting the pairing beyond what its own tier suggests.

The nearest rival CPUs show how close this i5-9400 is to its competition. The Intel Core i3-10305 scores 2300 in average benchmarks, just 0.2% behind the i5-9400's 2305. The Core i3-1125G4 also sits 0.2% behind, while the Intel Xeon E-2134 trails by 0.4%. The Core i7-8809G leads by 0.6% with a score of 2319. These deltas are tiny, meaning the i5-9400 is interchangeable with several other CPUs in terms of raw compute. The GPU side shows a similar pattern: the RX 6750 XT's average score of 35327 is 0.2% ahead of the RX 5600M, 0.3% behind the RTX 5070 Ti Mobile, 0.9% behind the Radeon 880M, and 1.3% behind the RTX 3080. This clustering suggests that the combo's mid-pack rank is driven more by the GPU's position than any CPU deficiency.

The rank of 839 means roughly half of all tested combos outperform this pairing in Doom. Given the game's 2016 release and its well-documented optimization, this is not a surprising outcome — the RX 6750 XT is a strong mid-range card, and the i5-9400 is a capable six-core processor, but neither is at the top of its class. Players with higher-end GPUs or newer CPUs will naturally see better results, but this combo remains competitive for its tier.

GPU Role — VRAM, clocks, and how they relate to this game's results

The AMD Radeon RX 6750 XT is built on the Navi 22 chip using TSMC's 7 nm process, with 17,200 million transistors packed into a 335 mm² die. Its RDNA 2.0 architecture provides 2560 shading units, 160 TMUs, and 64 ROPs, which translate to a 416.0 GTexel/s texture rate and 166.4 GPixel/s pixel rate. The GPU's FP32 throughput of 13.31 TFLOPS is the raw compute engine that drives Doom's rendering, and it scales predictably with resolution in the measured data.

Clock speeds play a clear role in the frame rates. The base clock runs at 2150 MHz, the game clock at 2495 MHz, and the boost clock reaches 2600 MHz. The 450 MHz difference between base and boost represents a 21% potential performance swing, and Doom's workload appears to engage the boost clock effectively — the 1080p Low result of 238.6 FPS demonstrates the GPU sustaining high throughput. The memory clock of 2250 MHz with 18 Gbps effective speed, paired with 12 GB of GDDR6 on a 192-bit bus, yields 432.0 GB/s bandwidth. This bandwidth is sufficient for 1080p and 1440p, but at 4K Ultra, the 53.7 FPS result suggests the memory bus becomes a constraint as texture data and framebuffer demands grow.

The 12 GB VRAM capacity is generous for a 2016 game like Doom, which was designed when 4 GB GPUs were common. Even at 4K Ultra, the game is unlikely to exceed 12 GB of VRAM usage, so capacity is not the limiting factor. Instead, the bandwidth and pixel throughput determine the 4K performance ceiling. The GPU's 40 ray accelerators are present but irrelevant for Doom, which does not use ray tracing. The 79th percentile ranking among all GPUs confirms this card is above average, and the measured FPS in Doom reflects that positioning — strong at 1080p and 1440p, adequate at 4K with settings tuned down.

Measured FPS Breakdown — resolution by resolution, settings by settings, exact numbers

At 1920x1080, the full settings sweep shows the GPU's headroom. Low delivers 238.6 FPS, Medium 209 FPS, High 177.4 FPS, and Ultra 143.4 FPS. The spread from Low to Ultra is 95.2 FPS, representing a 40% performance cost for maxed settings. The incremental drops are: Low to Medium loses 29.6 FPS, Medium to High loses 31.6 FPS, and High to Ultra loses 34 FPS. This near-linear degradation indicates that each quality tier adds a consistent rendering load, with no single setting causing a disproportionate hit.

At 2560x1440, the numbers compress. Low averages 158.7 FPS, Medium 137 FPS, High 115.6 FPS, and Ultra 92.5 FPS. The Low-to-Ultra spread is 66.2 FPS, smaller in absolute terms but similar in percentage (42% cost). The drops are 21.7 FPS (Low to Medium), 21.4 FPS (Medium to High), and 23.1 FPS (High to Ultra). This consistency suggests the GPU is handling the resolution increase uniformly across settings, without any particular preset becoming disproportionately expensive.

At 3840x2160, the performance envelope tightens considerably. Low produces 85.2 FPS, Medium 72.6 FPS, High 62 FPS, and Ultra 53.7 FPS. The Low-to-Ultra spread is just 31.5 FPS, and the percentage cost from Low to Ultra is 37% — slightly less than at lower resolutions. The drops are 12.6 FPS (Low to Medium), 10.6 FPS (Medium to High), and 8.3 FPS (High to Ultra). The shrinking absolute differences at 4K indicate the GPU is nearing its throughput ceiling, where each setting change has less absolute impact because the baseline frame rate is already low.

CPU Role — cores, clocks, and how they relate to this game's results

The Intel Core i5-9400 provides six cores and six threads, running at a 2.90 GHz base clock with a 4.10 GHz boost clock. This Coffee Lake processor, built on Intel's 14 nm process, has a 65 W TDP and supports dual-channel DDR4 memory with 42.7 GB/s bandwidth. In Doom, which is primarily GPU-bound at higher resolutions, the CPU's role is to feed the GPU with draw calls and game logic updates. The measured FPS data shows no signs of CPU bottlenecking — even at 1080p Low, where the GPU is least stressed, the system reaches 238.6 FPS without the CPU becoming a constraint.

The i5-9400's benchmark scores provide context for its performance tier. Its Cinebench R23 multicore score of 7969 and single-core score of 1125 place it at the 50th percentile among all CPUs. The multicore score of 3346 in Cinebench R20 and 803 in Cinebench R15 further confirm this mid-range positioning. The CPU's 9 MB of shared L3 cache and 256 KB L2 per core help with game asset streaming, but Doom's engine is not heavily dependent on cache size. The 4.10 GHz boost clock is the key differentiator for gaming — higher single-thread performance directly benefits frame pacing.

The nearest rival CPUs show how clustered this processor's performance is. The Core i3-10305, Core i3-1125G4, and Xeon E-2134 all score within 0.4% of the i5-9400, while the Core i7-8809G leads by 0.6%. These tiny deltas mean that swapping the i5-9400 for any of these alternatives would produce nearly identical Doom performance. The fact that the combo ranks 839th out of 1681 configurations, despite the GPU being in the 79th percentile, suggests the CPU is not the limiting factor — if it were, the rank would be closer to the GPU's percentile. Instead, the mid-pack rank reflects the combination's overall tier, where the GPU's strengths are balanced by the CPU's average standing.