Orion O6's PCIe x16 slot: Wattage, 12V Q

#1

Hi!

On the Orion O6’s PCIe x16 slot (which has 8 lanes of PCIe v4):

  • Does the PCIe slot have 12V power supply both when the SBC is powered by ATX, and by USB-C PD?

  • The documentation https://docs.radxa.com/en/orion/o6/hardware-design/hardware-interface#pcie-x16-slot- says when the SBC is powered " With USB－C PD power: Maximum power from the PCIe slot is 15W". Curious, if you power the SBC with USB-C PD and the PCI slot draws constantly 25W or 20W, what actually happens - will you over-burden some 12V voltage stepper and risk permanent damage, or should it supposedly be OK?

For clarity: To my best awareness, the specific PCI card I want to connect which draws 20-25 watts, mostly only draws 12V. I.e. it draws almost no 3.3V.

From the O6’s PCB design, does it look OK to draw 20-25 watts of 12V on the PCI socket when the O6 is powered via USB-C?

Thanks

O6 enclosure with one horizontal PCI x8/x16 slot?
#2

There would be no damage but since the 12V power is shared with the system, you will face stability issues when the system load is reaching the max(~30w).

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#3

@jack What voltage does the O6 negotiate to, is it to 12V or 20V? What if the USB-C power supply supports 4-5A at 20V or 4-5A at 12V, are there still issues when reaching 30W e.g. dependence on some voltage stepper onboard that has a 30W limit?

#4

I just check with the hardware engineer. The default negotiation voltage is 20V. If you feed 100W(20V/5A) from the type C, the 12V for PCIe is 5A max in theory. Our guide suggests a typical use case, which the O6 is powered by a PD 65W for the whole system, in this case, max 30W for the CPU, 20W for the SSD + USB devices, 15W for the PCIe slot.

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#5

Oh excellent. So if you power the O6 with 100W(20V/5A) USB-C PD, then internally of 12V the system will have 5A = 60W, of these 60W the motherboard takes 30W so there’s 30W for the PCI (+ SSD and any USB peripheral etc. to share).

So if the O6 is powered by USBC-PD 100W and it has no other SSD or peripherals but only one PCI card, then it is fine for that card to take 30W (all of it on the 12V lane). Great.


It sounds like O6 powered by USBC-PD 100W with one M.2 SSD and one PCI card that peaks around 20-25 watts could work. PCI peak 20-25W + an M.2 SSD can peak around 11W depending on model + the motherboard at 30W, it’s to really push it. One would need to make performance test with max CPU load and disk and network IO for a long time to see if it’s reliable.

I guess the 5A limit to 12V is the capacity of a voltage stepper on the motherboard.

Do the 3.3V and 5V voltage steppers take their power from the 12V, so therefore 3.3V and 5V are taken from the 5A (60W) budget of 12V, and that’s why the 60W limit will affect USB peripherals, SSD etc. also?

#6

Yes, 3.3V and 5V are also taken from 12V.

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#7

You should note that it negotiates max 65w via USB-C and that’s the bottleneck. If it would negotiate higher (I tried) then more would be possible.
I am able to run a GT1030 via USB-C power fine for desktop use and light gpu applications (~50w power draw combined) but I don’t want to risk system crashes and use a pico psu (with over 20% headroom) to be sure.

Good to know you wouldn’t do any permanent damage when using more than 15w on the pcie slot when powered via usb-c pd.

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#8

Or an AMD Radeon Rx6400 which consumes a maximum of 15w for me

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#9

@blondu Amazing.

In Linux on ARM, both Radeon and Nvidia is supported, right?

It’s only in Windows on ARM that only Radeon drivers exist, and there are no Nvidia drivers yet. Right

#10

I haven’t tried it in Windows ARM and Linux. It doesn’t work with the dedicated kernel 6.1.44, but it works in Fedora 41 with kernel from 6.14.8 up.
Nvidia I tried NVIDIA GeForce GT 1030 but it’s weaker…