3x 1080 Ti on x370 enough PCIe lanes?

[phongle123]

Hello, I own an Asrock x370 Taichi MB. I plan on getting 3 x1080 Ti (not for gaming).

 

Specs: 2 PCIe 3.0 x16, 1 PCIe 2.0 x16, 2 PCIe 2.0 x1

 

Ryzen 7 on x370 has 24 PCIe lanes which means I can run all 3 x 1080 Ti's in x8.

 

1) Does any of the motherboards built-in stuff (Wi-fi card, sound card, etc.) use any of my PCIe lanes?

 

2) If I run all 3 cards in x8 and I plug in for ex: an NVMe SSD x4. Will one of my GPUs drop down to x4 lane. So it will run x8, x8, x4 (GPU) and x4 (NVMe)?

 

3) Is there any way to control how many PCIe lanes each lane may use?

 

I saw this image in regards to 2).

[LukeSavenije]

1) yes, it will.

2) also, yes

3) as far as i know there isn't, but i've never used any asus or asrock boards

[phongle123]

3 minutes ago, LukeSavenije said:

1) yes, it will.

So that means that I'm already not getting my full 24 lanes to start off with since the MB perfs are using some of my PCIe lanes. Do you happen to know or how I can find out which perfs embedded on the MB is using PCIe lanes that I can turn off to obtain the full 24 lanes?

Meaning for 2) it will already be at x8, x8, x4, x# (MB stuff). Thus, if I add an NVMe, it will drop off to x8, x4 (GPU), x4 (GPU), x4 (NVME), x# (MB stuff)?

[LukeSavenije]

I actually don't know if your graphics card will drop to 4x or the nvme to 2x. I just use 16 lanes on my pc.

[Zagna]

Ryzen has 24 PCIe 3.0 lanes

• 16x for graphics, which on X370/X470 platforms can split to 8x/8x
• 4x for dedicated NVMe
• 4x for chipset connection
  • Chipset has 8 PCIe 2.0 lanes

 

1. PCIe peripherals will use chipsets PCIe 2.0 lanes
2. 2 GPUs will run at 8x PCIe 3.0, 1 GPU will run at 4x PCIe 2.0 from the chipset and your NVMe will run at 4x PCIe 3.0.
3. No

[Spotty]

11 minutes ago, phongle123 said:

I plan on getting 3 x1080 Ti (not for gaming).

If this is for a workstation system, why not look at X299 boards with Skylake X CPUs instead of X370? You'll get more PCIe lanes, quad channel memory on supported CPUs, and potentially better CPU performance*
^{*depends on the CPU and whether or not the tasks you are doing are [also] CPU bound}

[MyRigsBetterThanUrs]

You'd be much better off looking at the prosumer/ workstation offerings from intel or AMD, they will have the right amount of pcie lanes for you, rather than having to stress about not having enough

[phongle123]

18 minutes ago, Spotty said:

If this is for a workstation system, why not look at X299 boards with Skylake X CPUs instead of X370? You'll get more PCIe lanes, quad channel memory on supported CPUs, and potentially better CPU performance*
^{*depends on the CPU and whether or not the tasks you are doing are [also] CPU bound}

 

8 minutes ago, MyRigsBetterThanUrs said:

You'd be much better off looking at the prosumer/ workstation offerings from intel or AMD, they will have the right amount of pcie lanes for you, rather than having to stress about not having enough

I do not plan on upgrading thus I am simply using what I have. The reason for this thread. Therefore someone with knowledge in this area can give me the correct answer.

[ImNotThere]

1 hour ago, phongle123 said:

 

I do not plan on upgrading thus I am simply using what I have. The reason for this thread. Therefore someone with knowledge in this area can give me the correct answer.

Okay, the correct answer is that the x370 Chipset is a consumer level Chipset along with the Ryzen CPUs, this means they were not intended to use 3 GPUs and pcie based storage

 

You could use 2 1080tis with the pcie based storage 

 

What software are you using? Do you know how well it scales with multiple GPUs? Most software I have used scales incredibly poorly with more than 2 GPUs, some software scales horribly with anymore than 1 GPU

Hope this helps.

[phongle123]

12 hours ago, ImNotThere said:

Okay, the correct answer is that the x370 Chipset is a consumer level Chipset along with the Ryzen CPUs, this means they were not intended to use 3 GPUs and pcie based storage

 

You could use 2 1080tis with the pcie based storage 

 

What software are you using? Do you know how well it scales with multiple GPUs? Most software I have used scales incredibly poorly with more than 2 GPUs, some software scales horribly with anymore than 1 GPU

Hope this helps.

Yes, I scourged the forums and someone had 4x 1080 Ti's that did a comparison. 

In GPUs (1080 Ti) -- A tutorial scene given by the software to everyone.

1. 1m58s
2. 1m
3. 42s
4. 33s

Improvements, from GPU to GPU

1. > 2 = +97%; -58s; 58s total
2. > 3 = +43%; -18s; 1m16s total
3. > 4 = +27%; -9s; 1m25s total

Or, if cumulative (which I don't think people use this metric to compare improvements)

       1 > 2 = +97%

       1 > 3 = +180%

       1 > 4 = +358%

The first metric makes more GPUs look worse and worse since the 3rd GPU is comparing against 2 GPUs and the 4th GPU is comparing against 3 GPUs.

 

But the 2nd metric makes more GPUS look better, almost doubling each time. It also looks like 4 GPUs is off the charts if following the general assumption of 1 = +0%; 2 = +100%; 3 = +200%; and 4 GPUs = +300% but we peak at 4 GPU = +358%, 58% more than the +100%/extra GPU.

 

I'm debating if that 43% is worth it on top of 2x1080 Ti. This is just a small tutorial scene provided by the software developers.