Problems measuring power consumption with riser cards
It’s getting a bit tricky now, because PCIe 5.0 poses considerable challenges to signal integrity due to its high data transfer rates, especially in conjunction with additional components such as riser cables or internal connections within the graphics card. While previous generations of PCIe were more tolerant of signal interference, PCIe 5.0 requires significantly more precise signal transmission due to the doubling of the data rate to 32 GT/s. Any additional connection – be it a riser cable or an internal connection cable between the graphics card’s motherboard and its PCIe connector – can cause potential signal loss, reflections or distortions that affect stability.
A common problem is that such connections change the impedance of the signal system. These changes lead to reduced signal quality, especially with longer or poorly shielded cables. Another problem arises from the potential introduction of crosstalk between parallel lines if they are not sufficiently insulated. In practice, such interference manifests itself in instabilities such as boot problems, unexpected crashes or the inability of the system to initialize the graphics card correctly.
The discussion about riser cables and adapters shows that not only users but also development teams such as NVIDIA are struggling with the complexity of this issue. The experience with boot problems with the RTX 5090 in conjunction with riser cables or even NVIDIA’s first generation PCAT adapter (the new one did it so far) illustrates how critical signal integrity is for this hardware to function correctly. The problem is exacerbated by the fact that the Founders Edition internally utilizes a cable connection between the card’s motherboard and its PCIe connector, introducing additional resistance and potential signal loss. While this design decision may be made for aesthetic reasons, it leads to increased susceptibility to interference.
This leads to a fundamental debate about prioritizing design over function. While appealing looks and innovative form factors are important, “form follows function” should be the top priority. Technically, this means that hardware must be designed to perform optimally under real-world operating conditions before aesthetic considerations are taken into account. A design that compromises on signal integrity in favor of optical or mechanical stunts is not sustainable and can significantly impact the user experience. I ended up having to solder together a new solution, but what does the average user do who might want to install their card vertically in the case and use an additional riser cable?
Workaround: Set the PCIe version in the BIOS to Gen3 or Gen 4 and use either the iGPU or an older card for the boot process. The performance losses are around 10 to 15 percent for Gen 3 (out of the question) and between 0 and 4 percent for Gen 4. Or you can clock the bus down by 1 to 2 MHz.
Total power consumption and compliance with standards in practice
The power consumption in idle mode of around 16 to 19 watts shows that NVIDIA could also further optimize the drivers here. Under load, the measured values are within the expected range. In some demanding games, the maximum power consumption reaches up to 315 watts and is then slightly above the TDP limit. It is interesting that the power consumption is even more economical in lower resolutions such as Full HD and QHD. This could indicate improved efficiency in the use of resources in these modes, as the GPU requires less computing power to process the lower number of pixels. In addition, the use of DLSS, especially in combination with multi-frame generation (MFG), helps to further reduce energy consumption. The targeted reduction of the render load using AI-supported technologies noticeably reduces the load on the GPU without significantly affecting the image quality.
The mainboard slot, also known as the PCIe slot (PEG: PCI Express Graphics), is designed for a maximum current of 5.5 amps at a voltage of 12 volts in accordance with the PCI-SIG standard. This corresponds to a maximum power consumption of 66 watts, which can be supplied directly via the slot. The PCI-SIG standard serves as the basis for ensuring a uniform and reliable power supply via the mainboard slot while maintaining system stability. The specified limit value of 5.5 amps also takes into account short-term peak loads that can occur during abrupt load changes. However, these load peaks must not overload the system or affect other components due to voltage fluctuations.
A key advantage of this standard is that it ensures interoperability and compatibility between mainboards and graphics cards from different manufacturers. Clear specifications on the maximum load prevent potential damage to the mainboard’s conductors and connectors, which could be caused by excessive currents. The moderate load on the slot not only ensures system stability, but also increases the longevity of the hardware components concerned.
Another advantage of this limitation is the possibility of providing additional power supply via external connections to meet the requirements of high-performance graphics cards. The graphics card in question, which does not push the limits of the power supply even when using the modern 12V2X6 power connector design, demonstrates particularly efficient load distribution. The PEG slot is only loaded with a maximum of 0.8 amps, which corresponds to less than 10 watts. This minimal load on the mainboard slot underlines the efficiency of the card and significantly reduces potential thermal loads or damage to the mainboard. The card therefore not only contributes to system stability, but also demonstrates well thought-out energy management that optimally distributes the load between different power sources.
- 1 - Introduction and details of the Blackwell GB203-300-A1 GPU
- 2 - Test system and equipment
- 3 - Teardown: PCB, components and cooler
- 4 - Material analysis and heat conducting materials
- 5 - Gaming: Full-HD 1920x1080 Pixels (Rasterization Only)
- 6 - Gaming: WQHD 2560x1440 Pixels (Rasterization Only)
- 7 - Gaming: Ultra-HD 3840x2160 Pixels (Rasterization Only)
- 8 - Gaming: WQHD 2560x1440 Pixels, Supersampling, RT & FG
- 9 - Gaming: Ultra-HD 3840x2160 Pixels, Supersampling, RT & FG
- 10 - DLSS4 and MFG: Cyberpunk 2077 in detail
- 11 - DLSS4 and MFG: Alan Wake 2 in detail
- 12 - PCIe 5 problems, power consumption in practice
- 13 - Load peaks native vs. DLSS4, PSU recommendation
- 14 - Cooler, temperatures, thermography, noise
- 15 - Summary and conclusion







































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