Every generation, GPU's push performance further, delivering increasingly breathtaking visuals, higher frame rates, and unprecedented gaming realism. The jump from NVIDIA's RTX 4090 to the ROG Astral OC RTX 5090 brings not only extraordinary graphical capability but also an increased demand for power, reflecting gamers' relentless pursuit of maximum performance.
However, as energy prices continue to rise, efficiency matters now more than ever. Thankfully, there's performance waiting to be unlocked through careful tuning. By undervolting and fine-tuning your card’s voltage-frequency curve, you can achieve a better balance of performance, power usage, and thermal management.
This guide will demonstrate the benefits of optimising your ROG Astral OC RTX 5090, helping you get the most from your silicon while gaming, cooler, quieter, and smarter.
Test System
Before we get into the numbers, here’s the system used for undervolting and performance testing:
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Motherboard: ASUS ROG Crosshair X870E Hero
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CPU: AMD Ryzen 9 9800X3D
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Memory: 48GB (2x24GB) DDR5 @ 6400MT/s, CAS 28
Tuning your VF Curve
To tune our Voltage Frequency Curve, we need to install GPU Tweak III. To ensure you have the latest version, download from the Astral support site here
Flattening the Curve
Due to silicon variance, such approaches to vendors tuning the factory V/F curve without testing every card aren't practical, and some GPU samples may not be able to achieve a certain frequency depending on how low a given frequency or voltage we're targeting. Also, it should be assumed that most users have "paid for the whole VF Curve, so want to use the whole VF Curve". Thankfully, NVIDIA gives us access to each V/F point, allowing granular adjustment to tailor a curve that is befitting of what your silicon sample can do at a particular voltage point. By manually adjusting and flattening the voltage-frequency curve, we can temper the behaviour for a marginal performance penalty, instead of chasing every last megahertz.
This approach not only cuts power consumption significantly but also reduces thermals and keeps the card within a tighter performance envelope. The result? More efficiency, cooler operation, lower noise, and almost no perceptible performance loss.
Where Do We Draw the Line?
For gaming loads, RTX 5090 cards operate between ~850mV and 1.05v. Focus your adjustments within this range, as this is where most real-world performance occurs. In this configuration, my sample is comfortable at 2900MHz. Note that due to NVIDIA's GPU Boost behaviour, the effective boost clock will vary depending on the workload, thermal and power conditions.
If you wish to see even better efficiency benefits, you can set this lower. Make sure to test stability accordingly. 3DMark offers a stress test function for a number of it's benchmarks that help you monitor all manner of metrics of your GPU's performance and stability.
Fan Preferences - Cater for Your Environment
For my setup, I've opted for fixed fan speeds on the 5090 Astral Cooler. 50% on the side fans and 40% middle and rear fans.
After testing multiple combinations, this configuration proved optimal for my setup, consistently keeping the GPU cool and quiet under all workloads. The Astral's cooler is a monumental beast, so no need to push noise levels unnecessarily.
Slashing Watts, Not Frames
The results here speak for themselves. Our sample allows us to flatten our curve to 2,902 MHz from 950mV, resulting in a drastic reduction in power consumption for performance rivalling and sometimes surpassing the OC Mode on the Performance BIOS.
Massive Efficiency Benefits
Switching from the ROG Astral 5090's OC Mode to our newly created custom VF curve on the monstrous cooler design provides an average temperature drop of 10.37°C, proving just how effective voltage tuning can be. When we then apply that same custom curve to the Astral in conjunction with the custom water block, we see a further average improvement of 9.94°C. This is due to seeing a huge average power reduction of over 102W.
Frame & System Stability
For durability and stability testing, 3DMark provides invaluable stress-testing tools. By running 20 or more loops, we can monitor average frame rates and catch any signs of instability. With our fixed fan profile the GPU didn't exceed 66 °c after 20 loops of Steel Nomad, and our GPU frequency and frame rate remained consistent throughout.
Custom Water Cooling
Plumbing the ROG Astral RTX 5090 OC into our loop with an EKWB Quantum Vector³ waterblock, things only improve. Our water temperatures ranged from 25 to 34 °c during all of the conducted tests, with a fixed RPM on the radiator fans of 1,350RPM and 80% pump speed on the DCC.
Conclusion
Testing across several demanding games and benchmarks shows that undervolting the RTX 5090 using a custom voltage-frequency curve delivers an exceptionally efficient performance profile. Average frame rates remain very close to stock and OC Mode, typically within just one to three frames per second. Even in more sensitive titles like Monster Hunter Wilds, undervolted performance stays at around 97 to 98% of peak frame rates, confirming that very little performance is sacrificed in the process.
The thermal improvements are far more significant. In several workloads, edge temperatures drop by as much as 20 to 24 degrees. Titles like Time Spy Extreme, Monster Hunter, and Steel Nomad consistently show these reductions, thanks to the lower voltage and more stable boost behaviour under water. This also leads to substantial drops in power consumption. Depending on the title, the system draws between 70 and 170 watts less power. Cyberpunk 2077 and Monster Hunter stand out as the biggest winners here.
What’s most notable is how little these efficiency gains impact actual performance. In Port Royal, for example, the undervolted configuration delivers almost the same score as OC Mode while drawing over 125 watts less power. Even in lighter games like CS2, undervolting still reduces power by around 70 to 80 watts without affecting fluidity or responsiveness.
In short, a well-tuned undervolt makes the RTX 5090 significantly more power efficient and thermally controlled while maintaining its flagship performance level. It's an ideal solution for enthusiasts who want quieter operation, cooler temps, without giving up any of the top-tier experience.
Related Links
ROG Astral RTX 5090 - What Comes After the Summit
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