Asus B450-i question regarding M.2 slot and GPU

[beyondinfinity]

I was looking at this comparison table

https://www.reddit.com/r/sffpc/comments/9v20k7

What does it mean that one of the M.2. slots on this mother board is "shared with GPU" ?

I bought one of the Western Digital Blue 1TB SATA M.2 drives and an Asus 2060 RTX.
Will they be fighting for resources?

 

[Blaylock]

The Front (Heatsinked) M.2 slot has a dedicated connection to the Sata Contoller (shared with your other SATA ports) but will also use 4 lanes of the faster PCIe if a GPU is not installed (or possibly if it's not in use i.e. idle). The rear (non-heatsinked) M.2 slot can only use 4 lanes of your PCIe adapter so 4 of the available 16 lanes will get shared.

So are 12 lanes adequate for your GPU? That's a good question. The short answer is yes. The comparisons of running a GPU at 16 lanes vs 8 lanes (as measured in FPS) has a margin of difference of about 1%. Not a concern.

 

[beyondinfinity]

Well based on what you said and since I'm interested in the effect on machine learning I found this further information which indicated it may have a performance impact

https://www.reddit.com/r/homelab/comments/7v555a

 

[Blaylock]

Looking at just the numbers going for a PCIe3.0 x16 to a PCIe3.0 x12 should have a potential bandwidth of apx 12GB/s. Of course that's in a perfect world which we don't live in. Your actual performance will vary greatly and the largest factor, I would presume, would be the software used.

With that said, I'f you're looking for maximum throughput of PCIe lanes then you probably shouldn't be looking at a mITX board with it's single PCIe x16 slot. JMHO

 

[beyondinfinity]

Looking at just the numbers going for a PCIe3.0 x16 to a PCIe3.0 x12 should have a potential bandwidth of apx 12GB/s. Of course that's in a perfect world which we don't live in. Your actual performance will vary greatly and the largest factor, I would presume, would be the software used.

With that said, I'f you're looking for maximum throughput of PCIe lanes then you probably shouldn't be looking at a mITX board with it's single PCIe x16 slot. JMHO

Would a X570 itx board offer any improvement here compared to the b450?

Although I think I may have answered my own question after looking at this post https://www.gamersnexus.net/guides/3482-amd-x570-vs-x470-x370-chipset-comparison

 

[Blaylock]

Not for PCIe lanes. The issue with mITX boards are the single PCIe slot.

Looking back at your original post, Since the SSD you bought is SATA and not NVMe then this is really a moot point. Just slot it in the front M.2 location and it will run at SATA speeds and not share PCIe lanes, leaving all 16 for the GPU (or whatever you plug in there).