GPU - 4x 3080Ti Benchmarks / Anomaly (Octane & C4d 2023)

[corsac]

Hi!

I suppose it's gonna be hard to solve this just with the basic infos I have but let's hope..

I decided to make a setup with 4x 3080Ti (Founder Edition) to make a little render farm using Cinema4D and Octane.
All GPUs are recognized by my motherboard, displayed in my devices manager / in GPU-Z and all Updated drivers are installed. There is no SLI config.

But once I run the tests with OctaneBenchmarks (with RTX Enable), with all 4 GPUs activated I get a score of 1510.65.
4x 3080Ti is suppose to be a 2580 score if I look at the OctaneBench® 2020.1.5 Results. So it's almost half the score...

Based on that I tried several other tests by deactivating other GPUs one by one. I get :

- 3 GPUs activated (GPU 1, 2 and 3) : 769.89
- 2 GPUs activated (GPU 1 and 2) : 814.10
- 1 GPU activated (GPU 1 only) : 604.95

I precise that it is really when I have 3 or 2 or only 1 card activated! Not one at a time.
So that's where it gets weird. I get a better score when I only have 2 GPUs running rather than 3... And also almost get the same score when I only have one of them versus 3... So it feels like 1 (or multiple of these cards) was messing up something.

I decided to try every card indivually and here is the score I get for each of them.

- GPU 1 : 604.95
- GPU 2 : 506.81
- GPU 3 : 544.79
- GPU 4 : 640.48

So the scores for each card are ok compared to single card result on the OctaneBench® 2020.1.5 Results (which is 643 for the 3080Ti). Each card individual card seems to work okay.

Here are screenshots and CSV files of the tests : https://www.dropbox.com/sh/15vsmv629vhe ... o-tsa?dl=0
And here is some more infos about my config :

Motherboard : Gigabyte X299X AORUS MASTER (2 x PCI Express x16 slots, running at x16 and 2 x PCI Express x16 slots, running at x8)
CPU : intel Core i9 10920X 3.50 Ghz
RAM : 64Gb

The PCIE Slots on the motherboard are set at their respective max bandwith : PCIE x16 and PCIE x8. Here is how it look in the BIOS https://www.dropbox.com/scl/fi/h6ssdns2 ... gfqrh&dl=0
Don't know if that could be the issue.. The fact that not all PCIE are running at x16..

If any of you have an idea of what is going on, it could be a huge help. Because I don't get why I have correct scores for single cards but a bad score when running all of them.

Thanks a lot,
corsac

[boxfx]

My first instinct would be heat. The founders cards have a blow-through fan config, ie. the heat from the bottom card is blown straight through the heatsink into whatever is directly above it.... which is another card. What you've created is a wind tunnel of increasing heat. My main suspicion is that these cards with zero space between them are just overheating and throttling down.

To test for this, make a 3d scene where all visible parts are equally complex to render, maybe just a plane with dense noise and some absurd 200000 samples, then hit render. Watch the MS/s number and I bet you it starts off really high, then rapidly descends as the cards heat up.

On top of this of course install some gpu temp monitoring app, hwinfo, or afterburner.

Finally, what psu do you have?

[Tim_Twisted]

Does sound like a throttle issue as boxfx mentioned. Can you show a photo of the motherboard with the four cards installed? Also try running the benchmark with only GPU 1 and 3 installed, and physically remove the other two. That should at least increase the scores if heat is the problem.