Caldigit TS3+ - How many *independent* USB ports?

[theluggage]

The Caldigit TS3+ offers 5xUSB-A and 2xUSB-C - but how many of those ports are independent as opposed to sharing a single port with other devices via an internal USB hub?

Looking at "About this Mac -> System Report -> USB" should be informative as it should show up any internal hubs and whether the SD card, Ethernet, audio etc. are connected via internal USB.

Scenario: I've got a 2017 iMac and need more USB ports.

Obvious default solution would be a plain old cheap-as-chips USB3 hub - but that is just sharing 1 existing USB port between N ports. Using a TB3 dock like the Caldigit TS3+ instead adds extra USB controllers connected via 20Gbps TB3 which should be better....

I came across this StarTech 'multi channel' TB3-to-USB adapter online:
https://www.startech.com/uk/Cards-Adapters/USB-3.0/Hubs/thunderbolt-3-usb-3-1-hub~TB33A1C

... which superficially seems like an expensive way to get a 4-port USB hub - but the twist is that each port is independent - with its own controller, not shared with the other 3 ports - so its kinda in a different league.

NB: the price from other online resellers is substantially lower than on the Startech site, which is why I'm considering it...

...which brings me on to the actual question: The Caldigit TS3+ is more expensive, but superficially offers more USB ports - but are those all independent ports with potentially full bandwidth/low latency?

(I'm guessing the 10Gbps USB-C connector comes off the Thunderbolt controller chip).

I don't need the TS3+'s Ethernet or the power delivery (because iMac) and the front-facing SD slot is useful, but not essential. OTOH, the StarTech is cheaper, and because all of the USB ports are direct-to-controller, it could stand having another USB hub hung off it for 'mass connectovity'.

 

[joevt]

The ASM1142 used in the StarTech is limited by PCIe 2.0 x2 (8 Gb/s) or PCIe 3.0 x1 (7.87 Gb/s). The ASM1042A is limited to PCIe 2.0x1 (4 Gb/s). Both controllers support two ports each. The description says there are 3 USB controllers. That probable means the ASM1142 is connected using PCIe 2.0 x2, and that there are two ASM1042A. This adds up to the 20 Gbps of bandwidth they mentioned (though actual data is limited to 16 Gb/s and that's not considering PCIe protocol overhead). Therefore, the two USB 3.1 gen 2 ports are not independant.

There are faster USB 3.1 gen 2 controllers. For example, the Thunderbolt 3 port uses the USB 3.1 gen 2 controller built into the Thunderbolt 3 controller of the dock when a USB device is connected. The USB speed of the Thunderbolt port will be slightly faster than the USB ports of the ASM1142 because it will not be limited by PCIe 2.0 x2.

As for the TS3+, it's hard to say how it's put together without trying it out. A Thunderbolt controller in the dock provides 4 PCIe 3.0 lanes so you can connect up to four controllers (more would greatly increase the price).

The USB-C port must be separate from the Thunderbolt port, otherwise you could not use both of them at the same time.

The Ethernet could be provided by a PCIe controller or a USB adapter. The Audio and SD Card reader are probably USB. Maybe it has two four port USB 3.0 controllers, an ethernet controller, and a USB 3.1 gen 2 controller. If the USB 3.1 gen 2 controller uses two lanes, then the ethernet is provided by a USB adapter.

 

[popcorn-in-sac]

The Caldigit TS3+ offers 5xUSB-A and 2xUSB-C - but how many of those ports are independent as opposed to sharing a single port with other devices via an internal USB hub?

This is the closest information I have seen to what you are asking.

https://archive.caldigit.com/KB/index.asp?KBID=220&viewlocale=1

 

[joevt]

This is the closest information I have seen to what you are asking.

https://archive.caldigit.com/KB/index.asp?KBID=220&viewlocale=1

That makes things more clear:

1) Four port USB 3.0 controller, maybe a FL1100 (PCIe 2.0 x1, 4 Gbps) shared by audio and two USB ports. Is one port wasted - because I only count 3 devices? I hope #2 is a USB controller and not a USB hub connected to #1.

2) Four port USB 3.0 controller (probably same type as #1, 4 Gbps), shared by 3 USB ports and a USB SD card reader.

3) Two port USB 3.1 gen 2 controller (probably an ASM1142, PCIe 3.0 x1, 7.877 Gbps) shared by a USB-C port and a USB-A port. Why is the USB-A port marked as only 5 Gbps? Is that even possible if they're from the same controller?

4) Gigabit Ethernet controller.

 

[theluggage]

This is the closest information I have seen to what you are asking.

https://archive.caldigit.com/KB/index.asp?KBID=220&viewlocale=1

That's precisely the sort of info I was looking for, thanks.

This adds up to the 20 Gbps of bandwidth they mentioned (though actual data is limited to 16 Gb/s and that's not considering PCIe protocol overhead). Therefore, the two USB 3.1 gen 2 ports are not independant.

Hmm - so '4 high-speed independent USB ports' in the product description would be slightly economical with then then...

Thanks, folks. That helps.