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Low 12v PCIe slot voltage on new RM850x


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I noticed yesterday when looking through HWinfo64 that the "GPU PCIe +12V Input Voltage" drops down to 11.5~11.6v under load , and then slowly climbs back up to the 11.7v range. I know ± 5% is the acceptable amount of variance, but should this be happening to a gold certified 850w power supply? All of my other voltages look good. Yesterday I also experienced a display driver crash while in a game, so I'm wondering if this is related at all. 

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Are you utilizing a single PCIe power cable with the Pigtail connector to power your GPU? Or are you utilizing a separate PCIe Power Cable from the PSU per 8-pin power connector on your GPU?

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Just now, Corsair Notepad said:

Are you utilizing a single PCIe power cable with the Pigtail connector to power your GPU? Or are you utilizing a separate PCIe Power Cable from the PSU per 8-pin power connector on your GPU?

I'm using two separate PCIe power cables to power my GPU. 

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for the PCIE slot, it's a very imprecise sensor on the GPU that you can't trust 🙂 for indication only.

If i look in my rig, the motherboard receives 12.09V, and the GPU reads 12.236V, so i have some free energy going on from Nvidia.

The PSU measures and regulates its voltage to the 24 pin connector. So the motherboard 12V (which is also a very imprecise reading) is the sensor that you should trust the most. Here you're at 11,9 - 12V so it's fine.

If really that reading bothers you you can try to remove the GPU, and give the PCIE contacts a good clean with isopropyl alcohol.

I've had fingerprints totally disable PCI lanes so we never know, if you touched them when installing it.

 

But TBH, i wouldn't trust that voltage at all, besides, the bulk of the power comes from the two PCIE cables, not from the bus.

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19 hours ago, LeDoyen said:

for the PCIE slot, it's a very imprecise sensor on the GPU that you can't trust 🙂 for indication only.

If i look in my rig, the motherboard receives 12.09V, and the GPU reads 12.236V, so i have some free energy going on from Nvidia.

The PSU measures and regulates its voltage to the 24 pin connector. So the motherboard 12V (which is also a very imprecise reading) is the sensor that you should trust the most. Here you're at 11,9 - 12V so it's fine.

If really that reading bothers you you can try to remove the GPU, and give the PCIE contacts a good clean with isopropyl alcohol.

I've had fingerprints totally disable PCI lanes so we never know, if you touched them when installing it.

 

But TBH, i wouldn't trust that voltage at all, besides, the bulk of the power comes from the two PCIE cables, not from the bus.

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At some point overnight the voltage dropped to the lowest I've seen it....but if it's really innacurate i'll stop worrying about it. 

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your two PCIE cables and the motherboard 12V come from the exact same rail, they should have the exact same voltage but they read 200mV apart. So yea it's not that accurate at all.

To get back to my rig, my GPU generates electricity, and the GPU temperature is consistently 1°C cooler than the water in the loop which is awesome but illustrates that those values should be taken with a pinch of salt 😉

If you have instability, voltage is rarely the cause unless your PSU is too weak, too old, or you're using cable extensions.

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