Key Takeaways
1. The Asus RTX 5090 Astral LC operates at a standard 600-watt power limit, achieving 146 FPS in 3DMark Speedway with stable temperatures under 60 °C.
2. A hardware modification by Roman “der8auer” lowered the effective resistance, allowing power consumption to rise to 660-720 watts without limit violations.
3. After the mod, the GPU clock increased by 100-110 MHz, boosting performance to 152 FPS, and further voltage adjustments led to peak performance of 158 FPS.
4. The shunt modification showed that liquid-cooled GPUs could manage higher power loads (750-800 watts) effectively, unlike air-cooled models which may overheat.
5. Caution is advised for similar modifications on air-cooled models due to thermal risks; custom cooling solutions or unlocked BIOS options could further enhance performance but also increase risks.
The Asus RTX 5090 Astral LC, which is cooled by liquid, has been put through tests using a hardware-level shunt mod to see how much performance can be gained by changing the standard 600-watt power limit. Roman “der8auer” Hartung carried out this modification and provided thorough benchmarks, thermal readings, and electrical measurements using tools like GPU Tweak III, HWInfo, and an external power monitor.
Performance Overview
When it comes straight from the box, the RTX 5090 Astral LC operates at 600 watts under maximum load, achieving about 146 FPS in the 3DMark Speedway test, with core clock speeds nearing 2800 MHz and memory clocked at 1750 MHz. Thanks to its all-in-one cooler, the graphics card maintains core temperatures below 60 °C, although memory temperatures can reach up to 80 °C. The noise levels are also quite bearable because it does not have a blower-style rear fan like the air-cooled version.
Modifications Made
To break through the power limit, der8auer installed 5 milliohm shunt resistors in parallel with the GPU’s onboard 2 milliohm resistors. This adjustment lowered the effective resistance to about 1.4 milliohms, causing the power measurement system to underreport actual power consumption by around 30%. Consequently, the total power used by the card increased to between 660 and 720 watts without the GPU indicating any limit violations.
Results After the Mod
After applying this mod, the GPU core clock went up by approximately 100 to 110 MHz, resulting in a performance increase to 152 FPS. By further increasing the GPU voltage using GPU Tweak III, power consumption approached nearly 800 watts, which allowed for a peak performance of up to 158 FPS. This performance surpasses that of Nvidia’s professional-grade RTX 6000 Ada card, which is priced at over 10,000 USD. In the final tests, GPU clocks remained stable above 2950 MHz under load, while core temperatures hovered around 60 °C, and hotspot readings were not available due to Nvidia’s software restrictions.
Considerations and Risks
Even though the card handled these conditions well without thermal throttling, the current distribution across the 12VHPWR connector became less balanced, with pin 6 drawing close to 13.5 amps. The per-pin sensing feature provided by Asus’s telemetry was crucial for detecting these electrical strains.
This testing indicates that simple shunt modification can lead to significant performance improvements in the RTX 5090 LC, especially when dealing with liquid-cooled models that can handle 750 to 800 watts of continuous heat. However, der8auer warns against attempting similar modifications on air-cooled models, as they might not be able to manage the extra thermal load safely. A custom loop or an unlocked 1000 W BIOS could potentially enhance performance even more, but this also comes with much higher risks.
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