[SOLVED] PCIE lanes question for running multiple GPUs

[The007baron]

Hello all,

I have been searching the forums for days to find someone with a similar situation as mine, but mine seems to be pretty unique. So here goes:

I have a Ryzen 9 5950x paired with a EVGA RTX 3080 Ti FTW3, both water-cooled. Running on a Asus x570 CROSSHAIR VIII DARK HERO.

I recently upgraded from a 1080ti SLI config that i used for work and gaming. I used the cards individually for work with 5 monitors (4 1080p monitors connected to the card in slot 1, and a single 4k monitor connected to the card in slot 3). Yes, 5 screens is excessive, but I actually use all 5 for work. For gaming I would enable SLI and just run the 4 1080p monitors (3x1 surround).

When i upgraded to the 3080 Ti, i added an old GTX 1030 (passively cooled) to run in the 3rd PCIE slot to run my 4th auxiliary 1080p monitor. Then ran the 3 1080P and 1 4k monitors on the 3080ti. Its great for work, i have all 5 monitors running smoothly.

The issue is now with gaming. The 1st PCIE slot is locked at 8x, and the 3rd PCIE slot is running at 8x as well. What options do i have to adjust this without have to disconnect the GTX 1030 when i want to game?

Is it possible to force PICE slot 1 into 16x and lock PICE slot 3 in 4x? That would be ideal, but just dont know if its possible.

Before anyone suggests i get an intel CPU for the sake of integrated graphics to run the 5 monitor, yes i realize this would work. Swapping out CPU and MB at this point is not feasible.

Open to other options though if there are any out of the box thinkers that come along.

Thanks

 

[Eximo]

No, the bifurcation will always drop to 8x when the other x16 slot is active.

If you can manage to get the GT1030 into the last slot on the board, it would run through the chipset. So worst case a chassis that has 8 PCIe expansion slots.

 

[The007baron]

Thanks for your reply Eximo,

This is the setup I am currently using, GT* 1030 is sitting in the lowest PICE slot. Do i need to manually configure anything in the BIOS to enable this?

The part I dont fully understand is my benchmark scores. When i first got my card, i installed in in my HTPC running a 3600X, just to make sure everything worked. I ran 3DMark Time Spy with the following results

15 339 with NVIDIA GeForce RTX 3080 Ti(1x) and AMD Ryzen 5 3600X
Graphics Score: 19 183
CPU Score: 7 183

Clock frequency: 1,980 MHz (1,365 MHz)
Average clock frequency: 1,801 MHz
Memory clock frequency: 1,188 MHz (1,188 MHz)
Average memory clock frequency: 1,179 MHz
Average temperature: 48 °C


When i installed the 3080 Ti in my main machine i got the following results:
14 865 with NVIDIA GeForce RTX 3080 Ti(1x) and AMD Ryzen 9 5950X
Graphics Score: 17 006
CPU Score: 8 676

Clock frequency: 1,365 MHz (1,365 MHz)
Average clock frequency: N/A
Memory clock frequency: 1,188 MHz (1,188 MHz)
Average memory clock frequency: N/A
Average temperature: N/A

(including the GT 1030)

Not sure why i didn't get averages or temps on the second run.

My assumption is the graphics score differential of 2000 points due to the PCIE lane running at 16x for the first test and 8x for the second. Would that make sense or could there be something else at play? Again, i have the GT 1030 running in the last PCIE slot for the second test.

 

[The007baron]

Did some tweaking to the CPU and GPU, and got my score a bit better. Still under average (18361) for a 3080 Ti due to it running at 8x:

17 207 with NVIDIA GeForce RTX 3080 Ti(1x) and AMD Ryzen 9 5950X
Graphics Score: 18 323
CPU Score: 12 793

and the monitoring categories worked as well:

Clock frequency: 1,980 MHz (1,365 MHz)
Average clock frequency: 1,822 MHz
Memory clock frequency: 1,188 MHz (1,188 MHz)
Average memory clock frequency: 1,179 MHz
Average temperature: 50 °C

Slight bump to the graphics score, but the main increase was the CPU score.

I can live with this for the time being, I just feel like I am leaving a lot of performance on the table by running in 8x. Would be curious if there is anything I can do to optimize my setup.

 

[The007baron]

Now i have completely confused myself. I installed MSI afterburner and did a bit more tweaking and some how GPU-Z is now showing the 3080 Ti at PCIe x16 4.0 and the GT1030 at PCIe x4 3.0.

I don't understand, is this just an incorrect value in GPU-Z?

 

[hotaru.hino]

Now i have completely confused myself. I installed MSI afterburner and did a bit more tweaking and some how GPU-Z is now showing the 3080 Ti at PCIe x16 4.0 and the GT1030 at PCIe x4 3.0.

I don't understand, is this just an incorrect value in GPU-Z?

Gathering from the specs reported on the website and the manual, the third PCIe slot gets lanes from the chipset and maxes out at x4. GT 1030 doesn't need anywhere near 16 lanes to operate properly. Also the GT 1030 is wired as a 4 lane card, even if it looks like a 16 lane one.