Question: PCIE Gen3 x4 split into 2X PCIE Gen3 x2

[gmarti]

Hello,

I'm using an Odroid H4+ with frigate and would like to connect a dual edge tpu to it.

I ordered an M2 2x2 board to split the 4x Gen3 PCIE M.2 into two PCIE Gen x2
https://www.hardkernel.com/shop/m-2-2x2-card/
So that I can connect an SSD and the Coral TPU

It seems I would needs this board to use both TPU: https://www.makerfabs.com/dual-edge-tpu-adapter-m2-2280-b-m-key.html
Can I expect this setup to work ?

Then another question is about the documentation that states:
PCIe lane configuration:

• Upstream: x1 Gen2
• Downstream: 2 x1 Gen2

I would expect it to say:
PCIe lane configuration:

• Upstream: 1 bus 2 lanes Gen2
• Downstream: 2 buses 1 lane Gen2
  Because it splits 2 lanes into two buses ?

Otherwise there is a performance hit no ?

[pocki]

I got mine Dual Edge TPU Adapter today. As I see correct it's this ASM2806I chip

[magic-blue-smoke]

@gmarti thanks for your interest in adapter boards

It seems I would needs this board to use both TPU: https://www.makerfabs.com/dual-edge-tpu-adapter-m2-2280-b-m-key.html

Yes, this adapter should do the job

Can I expect this setup to work ?

This setup is expected to work. The only thing which is out of my control is power: Odroid SBC and adapter shall be able to deliver power for NVMe SSD and two TPU cores

Then another question is about the documentation that states: PCIe lane configuration: Upstream: x1 Gen2, Downstream: 2 x1 Gen2. I would expect it to say: PCIe lane configuration: Upstream: 1 bus 2 lanes Gen2, Downstream: 2 buses 1 lane Gen2. Because it splits 2 lanes into two buses ? Otherwise there is a performance hit no ?

PCIe adapter and m.2 BM adapter are using ASM1182e switch IC, which is one lane Gen2 upstream and two Gen2 x1 ports downstream. It works just like Ethernet switch IC, sharing upstream bandwidth between two downstream ports. Tests demonstrate no significant performance drop. Let me know if test results are needed here.

@pocki you're mentioning new Dual Edge TPU Adapter for two TPU cards which is using ASMedia ASM2806 Gen3 x2 PCIe switch IC, where PCIe bandwidth is not an issue. Good to hear it's finally reaching customers! Please let me know your impressions, even if it just works

[gmarti]

Thank you for the detailed explanation 👍

I just ordered we will see how it works

Thanks for doing this for us 💯

[pocki]

Sorry, I mixed up my browser tabs.
@magic-blue-smoke Thanks for the great work!