Are there any devices / hubs that can get around the 10gb USB upstream port limitation?

[MRxROBOT]

I’ve read that you can attach a TB3 dock to a TB4 hub or dock to get around the 10gb USB upstream port limitation but that’s a costly solution. Are there any docks / hubs / devices that can provide more bandwidth to USB devices that can be had at a reasonable price?

 

[MRxROBOT]

I daisy chained a TB3 dock to my TB4 Hub and can confirm that this does in fact give an addition 10gb upstream. Unfortunately this is a costly solution and doesn't make sense to scale to the other ports.

 

[joevt]

A TB4 dock is just a USB hub except when you connect downstream Thunderbolt 3 devices. There's no way around that.
The only peripheral TB4 chip is the Goshen Ridge. I think the USB layout is always: "one USB hub with 10 Gbps USB upstream and four 10 Gbps USB downstream ports" even if you are not using USB tunnelling (USB tunnelling happens on M1 Macs when the TB4 dock is connected first - you can disable USB tunnelling by connecting the TB4 dock downstream from a TB3 dock).

USB tunnelling means the USB controller of the M1 Mac is used to communicate with the USB hub in the TB4 dock.
Without USB tunnelling, PCIe tunnelling is used to communicate with the USB controller of the Goshen Ridge.
Now, I suppose in the PCIe tunnelling case, Intel could have made it so that the four downstream ports were not part of a USB hub - instead they could have been part of the Goshen Ridge USB controller itself - so then they wouldn't be limited to 10 Gbps USB total - they would be limited by the tunnelled PCIe - ≈22 Gbps. but I guess that would have added more complexity.
Maybe someone will make a superior USB4 controller chip.

 

[MRxROBOT]

A TB4 dock is just a USB hub except when you connect downstream Thunderbolt 3 devices. There's no way around that.
The only peripheral TB4 chip is the Goshen Ridge. I think the USB layout is always: "one USB hub with 10 Gbps USB upstream and four 10 Gbps USB downstream ports" even if you are not using USB tunnelling (USB tunnelling happens on M1 Macs when the TB4 dock is connected first - you can disable USB tunnelling by connecting the TB4 dock downstream from a TB3 dock).

USB tunnelling means the USB controller of the M1 Mac is used to communicate with the USB hub in the TB4 dock.
Without USB tunnelling, PCIe tunnelling is used to communicate with the USB controller of the Goshen Ridge.
Now, I suppose in the PCIe tunnelling case, Intel could have made it so that the four downstream ports were not part of a USB hub - instead they could have been part of the Goshen Ridge USB controller itself - so then they wouldn't be limited to 10 Gbps USB total - they would be limited by the tunnelled PCIe - ≈22 Gbps. but I guess that would have added more complexity.
Maybe someone will make a superior USB4 controller chip.

@joevt

You've got a technical level of understanding regarding thunderbolt that leagues ahead myself and most others. Is there a preferred method in daisy chaining a Thunderbolt 3 dock and a Thunderbolt 4 hub? Each dock / hub will have a 10Gb/s SSD attached, and one will have an additional thunderbolt cable connected to another Mac for a "Thunderbolt LAN" setup.

 

[joevt]

Is there a preferred method in daisy chaining a Thunderbolt 3 dock and a Thunderbolt 4 hub? Each dock / hub will have a 10Gb/s SSD attached, and one will have an additional thunderbolt cable connected to another Mac for a "Thunderbolt LAN" setup.

I'm not sure.
There's a couple considerations.
1) Devices further downstream will have higher latency and therefore have slightly less performance.
2) A Thunderbolt 4 hub connected to a Thunderbolt 4 or USB4 host will use USB tunnelling. That means the USB controller of the host is used for USB devices connected to the Thunderbolt 4 hub. This may have lower performance than if it was using the USB controller of the Thunderbolt 4 hub.

If you connect the Thunderbolt 3 dock first, then you don't get USB tunnelling for either SSD but a Thunderbolt 3 dock will usually have a 10 Gb/s USB port that is limited to PCIe 3.0 x1 speed (7.9 Gbps) instead of full 9.7 Gbps USB speed.

If you connect the Thunderbolt 4 dock first, then you'll get USB tunnelling for the USB SSD attached to that but the Thunderbolt LAN connection to the other Mac can be closer to the host and you can use the downstream Thunderbolt port of the Thunderbolt 3 dock for full 9.7 Gbps USB.

I think you have some benchmarking to do.

 

[MRxROBOT]

Thanks for your thoughts on this joevt. I'm immobile at the moment due to recent surgery. Should be able benchmark this out sometime in November. I'll come back here and share my findings when I have everything pieced together.