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I have a similar setup here running without issues: Ryzen 5950x, 128GB RAM, 4090 + 3090 (previously dual 3090s), AX1600i PSU

I don't use C4D. I use Standalone and Modo, but can confirm Octanebench runs without problems too. Here's a couple of things to check while troubleshooting:

1. Make sure you have 1 PCIe power cable per 8-pin connection on the card.
eg. If your 2 cards have 3x8-pins each, then you'll need 6 separate PCIe cables.

2. If you are using any of the dual pigtail cables, don't connect the second pigtail.
Technically, connecting a pigtail cable to 2 card connections might work fine on this PSU, but avoid it for now just to be sure.

This PSU can be controlled by Corsair iCUE and has some settings to try/check:

3. Go to iCUE > ax1600i > device settings. Make sure each cable is set to 40A/40% (the default).
NOTE: I'm using iCUE v4.23.137 because I noticed a bug in newer builds which can set the PSU OCP amperage to the lowest setting (20A/20%).

4. You can also try running the PSU in Single Rail mode. iCUE > ax1600i > device settings > Single OCP. This should not be needed though.

funk wrote:I have a similar setup here running without issues: Ryzen 5950x, 128GB RAM, 4090 + 3090 (previously dual 3090s), AX1600i PSU

I don't use C4D. I use Standalone and Modo, but can confirm Octanebench runs without problems too. Here's a couple of things to check while troubleshooting:

1. Make sure you have 1 PCIe power cable per 8-pin connection on the card.
eg. If your 2 cards have 3x8-pins each, then you'll need 6 separate PCIe cables.

2. If you are using any of the dual pigtail cables, don't connect the second pigtail.
Technically, connecting a pigtail cable to 2 card connections might work fine on this PSU, but avoid it for now just to be sure.

This PSU can be controlled by Corsair iCUE and has some settings to try/check:

3. Go to iCUE > ax1600i > device settings. Make sure each cable is set to 40A/40% (the default).
NOTE: I'm using iCUE v4.23.137 because I noticed a bug in newer builds which can set the PSU OCP amperage to the lowest setting (20A/20%).

4. You can also try running the PSU in Single Rail mode. iCUE > ax1600i > device settings > Single OCP. This should not be needed though.

Thanks, I'll try those.
I am going a little crazy because I can't get any work done. I'm trying to use Arnold but it's not my normal workflow and I can't get near the same look I'm used to.
This all started after I tried rendering C4D Pyro elements in Octane. I know it makes no sense but that was when the issue first appeared.

[quote="funk"]I have a similar setup here running without issues: Ryzen 5950x, 128GB RAM, 4090 + 3090 (previously dual 3090s), AX1600i PSU

As an aside... where did you score the 4090... I've been looking.

I'd try to change frequency of GPUs to lower. And also try to disable one GPU for testing and keep watching the temperatures. Also try some older WHQL studio drivers with clean install.

aoktar wrote:I'd try to change frequency of GPUs to lower. And also try to disable one GPU for testing and keep watching the temperatures. Also try some older WHQL studio drivers with clean install.

I've already tried that. Same results.
I think I have tried everything short of a complete System install.

Anim8me2 wrote:

aoktar wrote:I'd try to change frequency of GPUs to lower. And also try to disable one GPU for testing and keep watching the temperatures. Also try some older WHQL studio drivers with clean install.

I've already tried that. Same results.
I think I have tried everything short of a complete System install.

did you try to physically remove one GPU and try?

aoktar wrote:

Anim8me2 wrote:

aoktar wrote:I'd try to change frequency of GPUs to lower. And also try to disable one GPU for testing and keep watching the temperatures. Also try some older WHQL studio drivers with clean install.

I've already tried that. Same results.
I think I have tried everything short of a complete System install.

did you try to physically remove one GPU and try?

That was it.

So I have swapped both cards and they both work individually. I am guessing that despite my having a PSU rated for 1600w I am not getting full output. Would an additional PSU just for the GFX card be a common solution?

Anim8me2 wrote: That was it.

So I have swapped both cards and they both work individually. I am guessing that despite my having a PSU rated for 1600w I am not getting full output. Would an additional PSU just for the GFX card be a common solution?

I think there are some technical problems with power draw. But some tech peep will help you more by testing these.

The 1600 provides far in excess of the power needed for a 4090 + 3090, we run dual 4090 on a 1200 psu here, the realistic load is around 200-250w when rendering, it rarely exceeds 270w; the whole 4090 power draw numbers were all a bit overblown compared to what it actually uses. As someone else mentioned, I would check how you have the power cables set up. Officially pcie 8 pin cables are rated for 150 watts each, but the corsair ones are rated to 300+ watts, hence they can just pigtail the extra connector on the end and still work fine. That said, if you can, its nice to run a dedicated 8pin cable to each gpu input where possible just for extra headroom.

In your position my next steps would be:

Try a different physical pcie slot if possible, maybe one of them is unhappy, we recently spent weeks diagnosing a bad machine and it turns out a duff cpu was providing bad pcie lanes to the gpu depending what slot they were in.

Swap the location of the pcie power cables on the psu to different sockets, spread them out to grab power from different psu rails instead of clustering them all from the same area on the psu.

Run a full DDU driver uninstall and reinstall totally fresh.

Try disabling RTX in octane to see if this helps.

Anim8me2 wrote:As an aside... where did you score the 4090... I've been looking.

There seems to be plenty of stock here in Australia, so it's not a problem if you aren't picky about the exact model.

Anim8me2 wrote:I am guessing that despite my having a PSU rated for 1600w I am not getting full output. Would an additional PSU just for the GFX card be a common solution?

As boxfx mentioned, 1600w is plenty for your dual 3090s. It's possible the PSU is faulty, but it could also be other components (motherboard, CPU, or RAM). The only way to really know is by swapping out one by one with a known working part.

If you don't have access to extra parts for testing, you can also try using MSI afterburner to lower the power limit on both cards. Set it to about 70-80%. You lose very little performance in Octane (1-3%). I've done this in the past to keep things cooler and more power efficient too.

One last thought... Which motherboard are you using? I don't have any experience with TR motherboards, but some motherboards have extra 4/8-pin EPS connections and/or additional 6/8-pin PCIe connections for extra/stable power. Make sure you've connected all of these to your PSU, just to rule this out.