[SOLVED] Can I add a third one?

[Im_A_Blimp]

I have two GPUs in my PC. They are not SLI together, and they wont be. They are both running PCIe 8x. If I add a third GPU, will my other 2 be dropped down to 4x? Motherboard is Gigabyte X570 Aorus Master. CPU is 3900X. Let me know. Thanks

 

[k1114]

No. It would run 8/8/4.

 

[Im_A_Blimp]

No. It would run 8/8/4.

Ok. What's the best GPU I can get that wont be bottlenecked by X4? Asking for both NVidia and AMD????

 

[RTX 2080]

What are you using the third GPU for?

 

[Im_A_Blimp]

Well right now I have a 2080S and a 1660Ti. I want to be able to video render and game at the same time. I can do that. But I just want a 3rd gpu so I can run a 3rd GPU task in parallel. Anything that won't be bottlenecked by PCIe x4. Preferably nvidia

 

[RTX 2080]

I have a RTX 2080 and a RTX 2060 both running at PCIe 3.0 x8. I do folding@home on both GPUs most of the time and then I game on one while the other is doing folding@home the rest of the time.

What PSU/CPU/Hard Drive are you using?

I ask what PSU you have because obviously you want to make sure you have enough headroom to run that much hardware all at once.

I ask what CPU you are using because running folding@home on one GPU uses about 15% of my available CPU power (with occasional spikes), so it can slow me down a bit sometimes in CPU intensive games. This could be true of you when running two different rendering tasks in the background in addition to your game.

I ask what hard drive you are using because if you are using an NVMe SSD, then using that PCIe x4 slot is going to make your NVMe SSD and new GPU compete for system resources, slowing both down (I believe NVMe SSDs use the shared x4 lanes that also run to the x4 slot you are trying to use).

I don't know which GPU stops just short of saturating the PCIe 3.0 x4 interface, but I'm guessing your 1660 Ti would do just fine; you could stick it in the x4 slot and then after testing to see if it performs just as well as before, buy a new Nvidia GPU of your choice to take its place in the x8 slot.

 

[Im_A_Blimp]

I have a RTX 2080 and a RTX 2060 both running at PCIe 3.0 x8. I do folding@home on both GPUs most of the time and then I game on one while the other is doing folding@home the rest of the time.

What PSU/CPU/Hard Drive are you using?

I ask what PSU you have because obviously you want to make sure you have enough headroom to run that much hardware all at once.

I ask what CPU you are using because running folding@home on one GPU uses about 15% of my available CPU power (with occasional spikes), so it can slow me down a bit sometimes in CPU intensive games. This could be true of you when running two different rendering tasks in the background in addition to your game.

I ask what hard drive you are using because if you are using an NVMe SSD, then using that PCIe x4 slot is going to make your NVMe SSD and new GPU compete for system resources, slowing both down (I believe NVMe SSDs use the shared x4 lanes that also run to the x4 slot you are trying to use).

I don't know which GPU stops just short of saturating the PCIe 3.0 x4 interface, but I'm guessing your 1660 Ti would do just fine; you could stick it in the x4 slot and then after testing to see if it performs just as well as before, buy a new Nvidia GPU of your choice to take its place in the x8 slot.

Right now both my GPUs are in 8x. I want one more in 4x. CPU is 3900X. PSU is SeaSonic focusplus platinum 850W. SSD is Corsair mp600 PCIe 4.0 @ 5gbps

 

[RTX 2080]

Yeah, I'd say stick your 1660 Ti in the x4 slot and see if it bottlenecks while running one of your rendering tasks while gaming on your other GPU at the same time. Download hwmonitor to see whether the PCIe x4 bus is being saturated. Based on the maximum % utilization of the PCIe bus that you see, you can make your choice of third GPU accordingly. If it's too much, maybe a 1650 Super will work best. If you have bandwidth to spare, maybe a 2060 would work well.

Yeah, you should be fine from the PSU/CPU side of things. Hopefully your mp600's throughput won't be negatively impacted.

 

[Im_A_Blimp]

Yeah, I'd say stick your 1660 Ti in the x4 slot and see if it bottlenecks while running one of your rendering tasks while gaming on your other GPU at the same time. Download hwmonitor to see whether the PCIe x4 bus is being saturated. Based on the maximum % utilization of the PCIe bus that you see, you can make your choice of third GPU accordingly. If it's too much, maybe a 1650 Super will work best. If you have bandwidth to spare, maybe a 2060 would work well.

Yeah, you should be fine from the PSU/CPU side of things. Hopefully your mp600's throughput won't be negatively impacted.

Where does it show PCIe saturation in hwmonitor?

 

[RTX 2080]

Where does it show PCIe saturation in hwmonitor?

When you run it, it shows all your hardware in expanded form. Find the GPU in question, look under "utilization" and find "bus interface." If you leave the software on while you are gaming and rendering at the same time, you'll be able to populate your max utilization of your PCIe x4 bus.

 

[k1114]

Bus interface is vram not pcie. There is no way to measure pcie saturation without external hardware.

The m.2 is not sharing lanes.

You can have a 2080ti on a x1 and not bottleneck rendering depending on the software as if can be self contained on the gpu. Folding isn't but I don't have any concrete pcie scaling benchmarks. From what I've been told, pcie 4.0 x4 sees no bottleneck with a 2080ti.

 

[RTX 2080]

Bus interface is vram not pcie. There is no way to measure pcie saturation without external hardware.

The m.2 is not sharing lanes.

You can have a 2080ti on a x1 and not bottleneck rendering depending on the software as if can be self contained on the gpu. Folding isn't but I don't have any concrete pcie scaling benchmarks. From what I've been told, pcie 4.0 x4 sees no bottleneck with a 2080ti.

Good to know

 

[Im_A_Blimp]

Bus interface is vram not pcie. There is no way to measure pcie saturation without external hardware.

The m.2 is not sharing lanes.

You can have a 2080ti on a x1 and not bottleneck rendering depending on the software as if can be self contained on the gpu. Folding isn't but I don't have any concrete pcie scaling benchmarks. From what I've been told, pcie 4.0 x4 sees no bottleneck with a 2080ti.

I was told that a 2080ti can't even use PCIe4.0

 

[Wolfshadw]

I was told that a 2080ti can't even use PCIe4.0

It can use PCI Express 4.0. Be pretty dumb to release a high-end motherboard that cannot use any high-end graphic cards. :/

I think what was meant was that the RTX 2080 Ti cannot fully utilize the available bandwidth of PCI Express 4.0 (which is true). In fact, the RTX 2080Ti barely saturates the PCI Express 2.0 revision bandwidth @x16.

-Wolf sends

 

[RTX 2080]

I was told that a 2080ti can't even use PCIe4.0

This is true; all RTX 20XX series cards are PCIe 3.0. Perhaps he meant it theoretically.