Example single 8-pin to dual 8-pin GPU splitters should never be used
© Vik-off VIK-off has shown an RTX 5070 system with a melted GPU power cable, but this is not another case of the 12V-2×6 connector itself failing. The 16-pin connection appears to have survived. Instead, the damage occurred farther on the PCIe power cable. The system used one 8-pin PCIe connection with a passive splitter creating two 8-pin plugs , which were then connected to the GPU’s 16-pin adapter.
NVIDIA RTX 5070 has a 250W Total Graphics Power and it is recommended to have 650W power supply. NVIDIA’s installation guide explicitly requires at least two independent dedicated 8-pin PCIe cables when using its 16-pin adapter. The alternative is a native PCIe Gen 5 16-pin cable rated for at least 360W.
One 8-pin connector does not become two
There is an important distinction between the cable itself and the PCIe connector. PCI-SIG defines a GPU-side 8-pin PCIe connection for 150W, while a 6-pin connection is rated for 75W. Some properly designed PSU cables can carry much more than 150W. Corsair, for example, says its PSU-side 8-pin connections and pigtail cables can exceed 300W, but it still identifies the GPU-side PCIe 6+2-pin connection as a 150W connection.
© Vik-off 
© Vik-off This is why a separate passive 1x 8-pin to 2x 8-pin splitter is a bad idea. Two plugs at the output do not create another power source. Both sides of the RTX 5070 adapter were ultimately pulling through the same original PCIe 8-pin connection. The fact that the RTX 5070 is a 250W card does not make this configuration safe, and NVIDIA specifically calls for two independent cables.
VIK-off also questioned why the otherwise simple system was equipped with a Zalman 1000W power supply. A larger PSU rating cannot compensate for an incorrectly configured GPU power cable. In this case, the 12V-2×6 connector and adapter were not shown as the failure point. The upstream feed cable was the part that overheated and melted. This PSU has more than one PCIe connector, so there was no problem connecting two separate cables.
© Vik-off The lesson here is that third-party 8-pin-to-dual-8-pin splitters should not be used for GPU power. This should not be confused with native pigtail cables supplied and validated by PSU manufacturers. An 8-pin-to-dual-6-pin splitter at least keeps the nominal output within the same 150W budget, at 75W per connector, although 6-pin GPU power has effectively disappeared from the current GeForce RTX 50 generation. For an RTX 5070 using NVIDIA’s adapter, the correct setup is two dedicated PCIe 8-pin cables or a compatible native 16-pin cable.
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