3 ms·

Is there any way for two or more things to share the one lane? Like two or more of: SATA, Coral [0, 1], second Ethernet, USB3? I'm guessing no, but I'm not real

Is there any way for two or more things to share the one lane? Like two or more of: SATA, Coral [0, 1], second Ethernet, USB3? I'm guessing no, but I'm not real knowledgeable about this stuff. I think maybe the best you can do is dedicate it to USB3 and get everything you want in USB3 adapter form, just as you would with the non-compute module form. [0] https://coral.ai/products/accelerator-module https://coral.ai/products/accelerator-module [1] https://coral.ai/products/pcie-accelerator https://coral.ai/products/pcie-accelerator

zamadatix 6y ago
Sure, PCIe is packet based so PCIe switches are a thing. Just be aware this is a single PCIe 2.0 lane, it's already overburdened when you added the first USB 3 port. For the coral it's probably cheaper and just as good a fit to put a USB 2 hub chip on and wire up the B+M m.2 version through that.
- scottlamb 6y ago
  Hmm, interesting, thanks, and I see now there are PCIe expanders based on that idea. [1] I think the CM-4 + reference IO card + expander + PCIe versions of stuff I'd want are getting more expensive than makes sense (in comparison to say the ODROID-H2+ that has more built in and I'm finding hard to beat lately) but maybe someone will make a single IO board that's more appropriate for a NAS or NVR. This hackaday article [2] suggests the CM-4 would be good for that. I looked up those bandwidth numbers: USB 2 = 480 Mbit/s PCIe 2.0 = 4000 Mbit/s USB 3 = 5000 Mbit/s I keep looking for lower-cost machines for a fully-functional open-source NVR. I don't think I'd be likely to use more than 4000 Mbit/s between a couple SATA HDDs, a second Ethernet port, and a Coral or two. But the Coral can use more than 480 Mbit/s by itself. The USB accelerator product page [3] says "* Compatible with USB 2.0 but inferencing speed is slower." [1] https://www.amazon.com/Express-Switch-Multiplier-Expansion-adapter/dp/B01M64W87Q https://www.amazon.com/Express-Switch-Multiplier-Expansion-a... [2] https://hackaday.com/2020/10/19/new-raspberry-pi-4-compute-module-so-long-so-dimm-hello-pcie/ https://hackaday.com/2020/10/19/new-raspberry-pi-4-compute-m... [3] https://coral.ai/products/accelerator https://coral.ai/products/accelerator

zamadatix 6y ago

Sure, PCIe is packet based so PCIe switches are a thing. Just be aware this is a single PCIe 2.0 lane, it's already overburdened when you added the first USB 3 port. For the coral it's probably cheaper and just as good a fit to put a USB 2 hub chip on and wire up the B+M m.2 version through that.

scottlamb 6y ago
Hmm, interesting, thanks, and I see now there are PCIe expanders based on that idea. [1] I think the CM-4 + reference IO card + expander + PCIe versions of stuff I'd want are getting more expensive than makes sense (in comparison to say the ODROID-H2+ that has more built in and I'm finding hard to beat lately) but maybe someone will make a single IO board that's more appropriate for a NAS or NVR. This hackaday article [2] suggests the CM-4 would be good for that. I looked up those bandwidth numbers: USB 2 = 480 Mbit/s PCIe 2.0 = 4000 Mbit/s USB 3 = 5000 Mbit/s I keep looking for lower-cost machines for a fully-functional open-source NVR. I don't think I'd be likely to use more than 4000 Mbit/s between a couple SATA HDDs, a second Ethernet port, and a Coral or two. But the Coral can use more than 480 Mbit/s by itself. The USB accelerator product page [3] says "* Compatible with USB 2.0 but inferencing speed is slower." [1] https://www.amazon.com/Express-Switch-Multiplier-Expansion-adapter/dp/B01M64W87Q https://www.amazon.com/Express-Switch-Multiplier-Expansion-a... [2] https://hackaday.com/2020/10/19/new-raspberry-pi-4-compute-module-so-long-so-dimm-hello-pcie/ https://hackaday.com/2020/10/19/new-raspberry-pi-4-compute-m... [3] https://coral.ai/products/accelerator https://coral.ai/products/accelerator